The paper used the hydrological data witch comes from forest and non-forest basin of both forest hydrological test stations and the national general hydrological stations, and carried out contrast analysis. With regard to small watershed, the paper got the conclusional data on canopy interceptions, stemflows and ground losses, and made formulas in order to utilize these data. With regard to large watershed, the national hydrological stations were chosen on different forest cover rates when the geographical conditions were same or similar. Forest watershed make annual runoff increase when the drought index is less than 1.2. and decrease when the drought index is more than 1.2.