cJSON* xjson = cJSON_CreateObject();

    cJSON_AddItemToObject(xjson, "a", cJSON_CreateString("aaa"));
    cJSON_AddItemToObject(xjson, "b", cJSON_CreateNumber(1));

    cJSON *json_data = cJSON_CreateObject();
    cJSON *a_item = cJSON_CreateArray();
    cJSON_AddItemToObject(json_data,"c", cJSON_CreateNumber(2));
    cJSON_AddItemToObject(json_data,"d", a_item);

    cJSON_AddItemToArray(a_item, cJSON_CreateString("hello"));
    cJSON_AddItemToArray(a_item, cJSON_CreateString("world"));
    cJSON_AddItemToObject(xjson,"data", json_data);
    char *buf = cJSON_Print(xjson);
    printf("%s\n",buf );//{"a":"aaa","b":1,"data":{"c":1,"d":["hello","world"]}}
    free(buf);
    cJSON_Delete(xjson);

结果：

{
    "a":"aaa",
    "b":1,
    "data":{
        "c":1,
        "d":[
            "hello",
            "world"
        ]
    }
}