我改了下，但大部分主题还是你的建议：
#include<stdio.h>
#include <windows.h>
void test(int year, int m, int d);
int main()
{
    int year, cha, m, d,choose;
    printf("\n");
    printf("输入出生年份,月份及日期：");
    scanf("%d %d %d", &year, &m, &d);
    test(year, m, d);
    scanf("%d", &choose);
    if (choose == 1)
        main();
    else
        exit(0);
}
void test(int year, int m, int d)
{
    int choose;
    int cha;
    cha = (year - 1985) % 12;
    if (cha < 0)
        cha = 12 + cha;
    switch (cha)
    {
    case 0:printf("牛年,生肖：属牛\n"); break;
    case 1:printf("虎年，生肖：属虎\n"); break;
    case 2:printf("兔年，生肖：属兔\n"); break;
    case 3:printf("龙年，生肖：属龙\n"); break;
    case 4:printf("蛇年，生肖：属蛇\n"); break;
    case 5:printf("马年，生肖：属马\n"); break;
    case 6:printf("羊年，生肖：属羊\n"); break;
    case 7:printf("猴年，生肖：属猴\n"); break;
    case 8:printf("鸡年，生肖：属鸡\n"); break;
    case 9:printf("狗年，生肖：属狗\n"); break;
    case 10:printf("猪年，生肖：属猪\n"); break;
    case 11:printf("鼠年，生肖：属鼠\n"); break;
    }
    switch (m)
    {
    case 1:{if (d < 20)
        printf("星座：魔蝎座\n");
           else
               printf("星座：水瓶座\n");
        break; }
    case 2:{if (d < 19)
        printf("星座：水瓶座\n");
           else
               printf("星座：双鱼座\n");
        break; }
    case 3:{if (d < 21)
        printf("星座：双鱼座\n");
           else
               printf("星座：白羊座\n");
        break; }
    case 4:{if (d < 20)
        printf("星座：白羊座\n");
           else
               printf("星座：金牛座\n");
        break; }
    case 5:{if (d < 21)
        printf("星座：金牛座\n");
           else
               printf("星座：双子座\n");
        break; }
    case 6:{if (d < 22)
        printf("星座：双子座\n");
           else
               printf("星座：巨蟹座\n");
        break; }
    case 7:{if (d < 23)
        printf("星座：巨蟹座\n");
           else
               printf("星座：狮子座\n");
        break; }
    case 8:{if (d < 23)
        printf("星座：狮子座\n");
           else
               printf("星座：处女座");
        break; }
    case 9:{if (d < 23)
        printf("星座：处女座\n");
           else
               printf("星座：天秤座\n");
        break; }
    case 10:{if (d < 24)
        printf("星座：天秤座\n");
            else
                printf("星座：天蝎座\n");
        break; }
    case 11:{if (d < 23)
        printf("星座：天蝎座\n");
            else
                printf("星座：射手座\n");
        break; }
    case 12:{if (d < 22)
        printf("星座：射手座\n");
            else
                printf("星座：魔蝎座\n");
        break; }
    }
    printf("\n");
    printf("是否继续查询：1.继续 0.取消：");
}

再改下
#include<stdio.h>
#include <windows.h>
void test(int year)
{
    int cha;
    cha = (year - 1985) % 12;
    if (cha < 0)
        cha = 12 + cha;
    switch (cha)
    {
    case 0:printf("牛年 生肖：属牛\n"); break;
    case 1:printf("虎年 生肖：属虎\n"); break;
    case 2:printf("兔年 生肖：属兔\n"); break;
    case 3:printf("龙年 生肖：属龙\n"); break;
    case 4:printf("蛇年 生肖：属蛇\n"); break;
    case 5:printf("马年 生肖：属马\n"); break;
    case 6:printf("羊年 生肖：属羊\n"); break;
    case 7:printf("猴年 生肖：属猴\n"); break;
    case 8:printf("鸡年 生肖：属鸡\n"); break;
    case 9:printf("狗年 生肖：属狗\n"); break;
    case 10:printf("猪年 生肖：属猪\n"); break;
    case 11:printf("鼠年 生肖：属鼠\n"); break;
    }
}
void must(int m, int d)
{
    switch (m)
    {
    case 1:{if (d < 20)
        printf("星座：魔蝎座\n");
           else
               printf("星座：水瓶座\n");
        break; }
    case 2:{if (d < 19)
        printf("星座：水瓶座\n");
           else
               printf("星座：双鱼座\n");
        break; }
    case 3:{if (d < 21)
        printf("星座：双鱼座\n");
           else
               printf("星座：白羊座\n");
        break; }
    case 4:{if (d < 20)
        printf("星座：白羊座\n");
           else
               printf("星座：金牛座\n");
        break; }
    case 5:{if (d < 21)
        printf("星座：金牛座\n");
           else
               printf("星座：双子座\n");
        break; }
    case 6:{if (d < 22)
        printf("星座：双子座\n");
           else
               printf("星座：巨蟹座\n");
        break; }
    case 7:{if (d < 23)
        printf("星座：巨蟹座\n");
           else
               printf("星座：狮子座\n");
        break; }
    case 8:{if (d < 23)
        printf("星座：狮子座\n");
           else
               printf("星座：处女座");
        break; }
    case 9:{if (d < 23)
        printf("星座：处女座\n");
           else
               printf("星座：天秤座\n");
        break; }
    case 10:{if (d < 24)
        printf("星座：天秤座\n");
            else
                printf("星座：天蝎座\n");
        break; }
    case 11:{if (d < 23)
        printf("星座：天蝎座\n");
            else
                printf("星座：射手座\n");
        break; }
    case 12:{if (d < 22)
        printf("星座：射手座\n");
            else
                printf("星座：魔蝎座\n");
        break; }
    }
    printf("\n");
    printf("是否继续查询：1.继续 0.取消：");
}
int main()
{
    int year, cha, m, d, choose;
    printf("\n");
    printf("输入出生年份,月份及日期：");
    scanf("%d %d %d", &year, &m, &d);
    test(year);
    must(m, d);
    scanf("%d", &choose);
    if (choose == 1)
        main();
    else
        exit(0);
}