By using a 3D convective cloud model,a hail-producing convective weather process on 23th August 2001 in Beijing is simulated and analyzed with cloud-seeding process.The results show that no matter the seeding agent is silver iodide(AgI) or liquid carbon dioxide(LC),the seeding effect in the region of maximum supercooled water(temperature range: 0—-10℃) is better than that in the region of maximum updraft(temperature range: 8—-7℃);and the seeding effect on both rain enhancement and hail suppression in the region of maximum supercooled water by AgI is better than that by LC,while in the region of maximum updraft,the seeding effect on rain enhancement by LC is better than that by AgI,but it is worse on hail suppression.For the studied case,no matter what seeding method is used,the earlier the seeding time,the better the effect on both hail suppression and rain enhancement with an appropriate seeding dose.In addition,the seeding effect on both hail suppression and rain enhancement could be poistive before the mature stage of cloud development,and the negative effects such as hail increase and rain decrease could occur while seeding during or after the mature stage.