#include<stdio.h>
struct student
{ int num;
  char name[10];
  char sex;
  char native[10];
  float grade;
} stu;
int main()
{char s[10];
 printf(" 1 student's number:");scanf("%d",&stu.num);
 printf("1 student's name:");scanf("%s",stu.name);
 printf("1student's sex:");scanf("%c",&stu.sex);getchar();
 printf("1 student's native:");scanf("%s",stu.native);
 printf("1 student's grade:");scanf("%f",&stu.grade);
 printf("%d,%s,%c,%s,%.2f\n",stu.num,stu.name,stu.sex,stu.native,stu.grade);//就是这不能正常输出stu.sex项
 return 0;
}

printf("1student's sex:");scanf("%c",&stu.sex);getchar();
删除getchar();就行了

不明白楼主为什么要多加一个getchar（）那个没必要的

它是用于清除缓存

printf("1 student's name:");scanf("%s",stu.name);getchar();
应该是这样的

#pragma warning(disable:4996)

#include<stdio.h>

 struct student
 {
    int num;
    char name[10];
    char sex;
    char native[10];
    float grade;
 } stu;


 int main()
 {
     char s[10];
    printf(" 1 student's number:");
    scanf("%d",&stu.num);
   
    printf("1 student's name:");
    scanf("%s",stu.name);
    getchar();

    printf("1student's sex:");
    scanf("%c",&stu.sex);
   
   
    printf("1 student's native:");
    scanf("%s",stu.native);
   
    printf("1 student's grade:");
    scanf("%f",&stu.grade);
    //printf("%3.2f",stu.grade);
   
    printf("%d,%s,%c,%s,%3.2f\n",stu.num,stu.name,stu.sex,stu.native,stu.grade);//就是这不能正常输出stu.sex项
return 0;
 }

printf("1 student's name:");scanf("%s",stu.name);

你這一步輸入的名字太長了，超過了10個字符？

#include<stdio.h>
struct student
{
    int num;
    char name[10];
    char sex;
    char native[10];
    float grade;
} stu;
int main()
{
    char s[10];
    printf(" 1 student's number:");scanf("%d",&stu.num);
    printf("1 student's name:");scanf("%s",stu.name);getchar();
    printf("1student's sex:");scanf("%c",&stu.sex);
    printf("1 student's native:");scanf("%s",stu.native);
    printf("1 student's grade:");scanf("%f",&stu.grade);
    printf("%d,%s,%c,%s,%.2f\n",stu.num,stu.name,stu.sex,stu.native,stu.grade);//就是这不能正常输出stu.sex项
    return 0;
}