Abstract: Based on the L－wave band sounding data conventional observation data and physical quantity，the paper carries out statistical analysis on the 49 rainstorms at the Wenchuan area and Maoxian area in Aba prefecture．The study results show that before the heavy rain comes，the lower the direction of the wind at the middle and lower level presented veering structure，the specific humidity and θse had been significantly increased and were higher than monthly average，there was obvious water vapor convergence existing in the northwest of the basin，northerly wind prevailed in the southern Gansu province，and there was northerly wind more than 10 m/s or higher in the southern basin．Based on the above indicators，the concept model of the rainstorms during July and August is established with a the fitting rate reaching 60%．