Taking Zhainugou small watershed for e}:ample,this paper deals with the guiding thinking of the matching model of forests and grasses in the comprehensive control of small watershed。In an overall layout，the multiple constraints should be taken into account, The suitable trees and grass species and their matching models for various establishing conditions have been screened in accordance with the ecological adptability of various tree and grass species. Also, the paper discusses the matching of forests and grasses in the comprehensive control of small watersheds in the semiarid loessal hilly areas.