In the rainfall process there are many factors which can effect runoff and infiltration.On the basis of data from 15 simulated rainfalls,this article received several conclusions as follows:(1)As far as the effect on runoff and infiltration is concerned,rainfall intensity is the crucial factor which could be influenced by increase of cover ratio mostly with the comparative decrease of runoff and increase of infiltration.(2)Effect of gradient on runoff and infiltration can also be influenced by rainfall intensity,in other words,the effects of these factors will be influenced and promoted each other,and the finally effect will be stronger than the numerically sum of each sole effect.(3)There are different modes of effect on runoff and infiltration owing to different form reasons of cover ratio.For example,different growth periods and different plant characters will weaken the effect of biology cover ratio on runoff and infiltration.