In order to understand the effect of the twice artificial precipitations by air-craft in 1990,the non-parameter techniques by W-M-W(Wilcoxon-Marn-Whitney)and Wilcoxon are used. The results show that the rainfalls vary in great amount between the plume area and non-plume area in 3 hours since operating. And the significant variations are also found in the plume area between 3 hours after and 3 hours before operating. Therefore,it is easy to understand that artificial seeding brings out the significant increment of rainfall. The rainfall inhencement are estimated quantitatively.