The nonstatic mesoscale model ARPS (Advanced Regional Prediction System) with detailed microphysical processes is used to simulate typhoon Wipha (2007), and the data of numerical simulation are used to analyze the microphysical structures and the precipitation forming mechanisms of the storm near typhoon eyewall. It is found that the ice phase microphysical processes are the main mechanism that initiates and produces the storm rain. Ice crystals can be produced by cloud water homogeneous nucleation, or cloud ices are produced by cloud water nonhomogeneous nucleation at heights 9000-14000 m. The ice grows into snow in 3 main microphysical processes (psfi, praci and piacr, which are defined in body text). The graupel is produced in 4 main microphysical processes (piacr, psacr, praci and pgfr). The graupel grows mainly in 2 main microphysical processes (dgaci and dgacw). The melting graupel and snow produce rain through accretion with cloud water in warm cloud. The production and growth microphysical processes of graupel play important roles in the precipitation forming mechanisms. There is not obvious difference of ice conversion ratios between two precipitation centers at （29.5°N，121.8°E） and （28.3°N，120.4°E）. But the ice grows more quickly into snow and graupel in terms of Bergeron process at （29.5°N，121.8°E） than at （28.3°N，120.4°E）. Then the precipitation particle can grow more quickly at (29.5°N, 121.8°E) than at （28.3°N，120.4°E） due to higher cloud water conversion ratios at low altitudes. There fore the rain conversion ratios are higher at （29.5°N，121.8°E） due to better configuration of clod and warm cloud processes.