Abstract:A new concept, forest coverage of the optimum forest protective effect(FCFP), is defined,and the theory and methodology to establish the FCFP are presented. On the basis of the given forest areas,the increase of the forest internal quality and the optimization of space distribution pattern have significant gains in protective effects of forest ecological system. The optimization of forest area, quality and space distribution maximize the forest protecting capacity(FPC). A maximum of FPC is regarded as FCFP,but the magnitude of FCFP is affected by a given natural environmental conditions. Based on the data from the region of low mountains and hills in Sichuan Basin,FCFP for districts of middle-low mountains, low mountains, hills, hillocks and plains may reach 57%, 46%, 44%, 31% and 13% respectively.