Based on the late years' data of forest resources, climate, hydrology and atmosphere in Jinggang Mountain region and by the methods of canonical correlation analysis and multiple linear stepwise regression, this paper analyzed the influence of forests on the climate, water quality and atmosphere of this region. The results showed that forest volume had an evident effect on maximum daily precipitation, extreme highest air temperature and atmospheric SO2 concentration, and on COD(cr) and ammonic nitrogen contents in river water. The greater the regional forest volume, the less maximum daily precipitation and the lower extreme highest air temperature, atmospheric SO2 concentration and water COD(cr) and ammonic nitrogen contents. Forest cover percentage could remarkably affect soil erosion modulus and atmospheric NOx concentration: the two latter were decreased as forest cover percentage increased. These results will provide theoretic foundation for the evaluation of the environmental value and ecological benefit of forest.