For the general problem of rainstorm under complex terrain，the use of isobaric coordinates can not accurately analyze and predict the intensity and movement of mountain rainstorm due to the intersection of the lower troposphere isobaric surface and the ground. In order to improve the rainstorm prediction level under complex terrain conditions，it is necessary to develop a set of rainstorm prediction methods under the terrain following coordinate system，which can not only directly reflect the terrain impact in physical quantities，but also avoid the differences in dynamic analysis of different regions caused by terrain in local rectangular coordinates or isobaric coordinates. Taking the second-order moist potential vorticity in the ensemble dynamic factor heavy rainfall forecasting method as an example，this paper studies and attempts dynamic heavy rainfall forecasting under the terrain-following coordinate system. It derives the mathematical form of the second-order moist potential vorticity in the terrain following coordinate system，and then explores the physical information contained in the secondorder moist potential vorticity in the terrain following coordinate system and the possibility of improving the precipitation forecast through case analysis and comparison with the second-order moist potential vorticity in the iso‐ baric coordinate system. Furthermore，the analog method is introduced to conduct forecast verification on quantitative precipitation forecasting using the second-order moist potential vorticity in the terrain-following coordinate system. The verification results show that in the ETS score of summer precipitation forecast in 2016 and 2017， The score of precipitation similarity correction method based on topographic second-order moist potential vorticity is higher than that of original forecast precipitation of GFS model.