Based on meteorological data, socio-economic data and geographic information data, this paper constructs a grid of 0.01 ° and combines with the theory of natural disaster risk assessment to make a detailed risk assessment and zoning of flood disaster in Harbin main urban area from three aspects : risk, exposure and vulnerability. The results show that the risk of flooding in the main urban area of Harbin gradually increases from northwest to southeast, and the southern part of Xiangfang ,the intersection of Songbei, Daoli, Nangang ,Daowai are the most seriously affected by flood; The exposure is high in the center and low in the surrounding areas, and the high risk is mainly located within the expressway around the city; The road network is densely fragile. The flood risk gradually increases from northwest to Southeast, and the East is significantly higher than the West. High-risk areas are located in the city center, western Daowai and most of Xiangfang District. The maximum process precipitation in the high-risk area is 215.4mm, which is located in the center of the city, the western part of the Daowai and most of the Xiangfang, where flooding is the most serious.