China postal code adopts 4-level 6-digit coding system, with the first two digits representing the province, that is, the number 2 1 representing Jiangsu Province, the third digit representing the city and the fourth digit representing the county, that is, the number 0 representing Xuanwu District, and the last two digits 23 representing the processing center of this city. This postal code represents the mailing address of Xianlin Avenue 163, Qixia District, Nanjing.