Abstract: In order to study the atmospheric circulation characteristics of rainstorm at 500 hPa in Hunlun Buir and to guard against the impact on agriculture from flood disasters caused by rainstorm, the atmospheric circulation background of the rainstorm cases were classified by utilizing the daily precipitation data of 16 stations and NCEP grid reanalysis data in Hulun Buir City between 1971 and 2010. The result showed that: the rainstorm cases were approximately classified into 4 types: (1) the direct interaction between subtropical high and westerlies zone system (71 cases,43.3%); (2) the long distance interaction between subtropical high and typhoon with westerlies zone system (35 cases,21.3%); (3) the long distance interaction between typhoon or tropical cyclone and westerlies zone system (27 cases,16.5%); (4) the directly action by westerly zone system (31 cases, 18.9%).