Based on the conventional meteorological observational data， automatic observational precipitation and 1°×1° NCEP FNL reanalysis data of time resolution of 6 hours interval， two heavy rain processes occurred on 1 August 2017 and 2-3 August 2018 in Heilongjiang province by the warm front frontogenesis north of the subtropical high are diagnosed with dynamic diagnosis method and synoptic method.The major conclusions are as follow： There are typhoons during the two warm front rainstorm， which cause the position of subtropical high to the west and north.The southwest low level jet outside the subtropical high transports a large amount of warm moist air with high momentum to the north.The two rainstorm processes are closely related to the high and low air jet.In the process of "0803"， the low-altitude jet stream is stronger， and the rainstorm area is located in the ascending branch of the vertical secondary circulation formed by the coupling of low-altitude jet stream and low-altitude jet stream.Before the rainstorm， the atmosphere is characterized by convective instability.The interaction of convergence uplift and secondary circulation updraft triggers convection and releases unstable energy， resulting in heavy precipitation.During the process of "0803"， the atmosphere is shown as convective stability during the rainstorm.The condition symmetry instability of the middle layer in the frontal region is beneficial to the enhancement and maintenance of precipitation intensity.In this process， the frontal intensity is greater， and the upward movement formed by frontal convergence is broader， resulting in heavy precipitation in a larger range.The release of latent heat of condensation over the rainstorm area will cause the generalized high potential temperature region to extend downward， and the wet baroclinic property of the middle and lower layers will increase significantly.The moisture divergence flux and the moisture vertical helicity can well describe the process of heavy precipitation.The strong precipitation area corresponds to the positive region of the moisture divergence flux and the negative region of the moisture vertical helicity.