An ever-increasing of atmospheric N deposition and P fertilization in the world significantly affect forest soils. Castanopsis fissa is one of the important timber species in southern China. Elucidation of the effects of N and P addition on C. fissa plantation ecosystems can provide theoretical guidance for the sustainable management of C. fissa plantations. In this paper, a field experiment was conducted to investigate the response of forest ecosystem to the increased N and P deposition in a 14-year-old Castanopsis fissa plantation in Yunyong Forest Farm, Guangdong province. Treatments included CK, N, P, and N+ P addition groups at doses of 0, 200 kg N, 80 kg P and 200 kg N+80 kg P (hm^-2·a^-1), respectively, with eight replicates per treatment. The results indicated that N addition decreased the total P, total K and effective K and increased the alkalized N in the soil. Addition of P increased soil organic matter, total N, total P, effective P, and effective K and decreased total K. Addition of N+P increased soil organic matter, total N, total P, alkalized N, and effective P and decreased total K. Addition of N, P, and N+P increased the number of soil bacteria and fungi and the activities of soil urease and acid phosphatase. Moreover, addition of P increased the number of soil actinomycetes and urease activity and addition of N+P also increased soil urease activity.