Based on statistical analysis of observed data of experiment of water and soil runoff plots at Xifeng soil and water conservation station from 1964 to 1980,it is proved that there is a very close corelation (y=aH^b )between individual rain fall erosive modulus and depth of runoff,which is a power funetion. The unit individual runoff depth (KW )was as soil anti-scour index which was used to evaluate the faetors affecting soil anti-scourability.