Abstract: Typhoons 8407, 8411 and 8504 are simulated with the PSU/NCAR mm4 model, then band-pass filtered flow field obstained from model output are analysed. It is found that there are strong convergence at the low layer of troposphere and marked divergence at upper layer over large area heavy rainfall causing by moist typhoon, while no mesoscale divergence at upper layer of troposphere occured over weak rainfall region causing by dry typhoon. In second part, the rapid enhancement of heavy rainfall caused by typhoon 8407 is simulated for comparison and the band-pass filtered stream field are analysed. The results show that large-scale environmental field of typhoon is the main source causing mesoscale systems or structures and latent heat release and topograpic effect are forming and affecting factors of mesoscale systems and mesoscale structure.