Using the GRAPES model which incorporates a new two moment microphysical scheme, two aircraft artificial precipitation processes that happened in Chongqing on 15 December 2010 are simulated and analyzed. The results show that GRAPES model is able to simulate the real synoptic situation of medium, the precipitation area is credibility, but the intensity is small. Seeding simulation has good correspondence with the observed rainfall in heavier precipitation areas. Seeding twice leads to the increasing of precipitation, the 24 h average enhancement rainfall is 3-5 mm and the maximum amount is 7 mm. The 24 h accumulative total precipitation of seeding is double times than no seeding in seeding area. Obvious enhancement result is seen in 1-2 hours after seeding, and the rain enhancement continues about 4 hours. At the beginning the area of enhancement is the same as the seeding area, spreading near the seeding area with the time. After the first seeding, the liquid water is quickly transformed into solid water by seeding ice crystal, and the vapor inflow accelerates changing into liquid water, so the liquid water quickly restore. There is no rain reduced. After the second seeding, the solid water increases by vapor transforming, the supplement of liquid water is poor, the ascending motion of clouds decreases, and the rainfall is reduced at the stage of natural precipitation.