Nnumerical simulation research on silver iodide (AgI) cold cloud seeding is conducted, focusing on the precipitation process that happened in North China from 9 to 11 May 2014. The WRF model coupled with silver iodide cold cloud catalytic module is used and the model parameter settings are based on actual artificial precipitation operations. The effect and mechanism of the precipitation are discussed and then two sensitivity tests on operation height and catalyst content are carried out. The results show that seeding appropriate catalyst content of AgI at about 5-6 km height and temperature of -20--15℃ can make ground precipitation increased significantly. Ground rain enhancement begins at about 30 minutes after seeding operation, and 70 minutes to reach the maximum, while rain reduction occurs after 90 minutes, and 110 minutes later the reduction of rain is more than the increase of rain. The main mechanism for precipitation is as follows. The AgI seeding makes the cold water content above〖JP2〗 the melting layer in cloud remarkably reduced, snow and ice content increased, and coalescence processes of rain and snow and rain capture cloud droplets enhanced. Increased snow crystals fall into the warm zone and melt into raindrops, then the rainfall significantly increases. Regarding the magnitude of microphysical processes, the snow particles’ melting is the main process leading to increased precipitation. Results of the two sensitivity tests show that the catalytic effects are better when seeding in clouds with rich supercooled cloud water, low temperature and low ice crystal content， and increasing the amount of catalyst could have better seeding result.