16 1600。 According to the information of China Postal Code Library, Keshan County is located in the northeast of Qiqihar City, Heilongjiang Province, and its postal code is 16 1600. Keshan County is located in the hinterland of Songnen Plain, one of the three black soil belts in the world. It is rich in agricultural products such as potatoes, soybeans and corn. It is the hometown of potato seeds in China and high-protein soybeans in China.