In the Ecological Experimental Station of Red Soil of Chinese Academy of Sciences, a six-year (1991~1996) stationary experiment had been carried out on a red soil slope land with different forests to study systematically dynamic circulation of N, P and K and establish a compartment model of nutrient circulation. The results indicate that a major part of N, P and K was stored in the soil compartment in different forest lands, amounting to above 97%. The annual total net accumulation of N, P and K was positive for six-year old broadleaf forest and conifer forest, being 36.51 kg hm^-2 and 29.70 kg hm^-2, respectively. The entire system was gaining in nutrient reserve, and N, P and K were all accumulating, showing surplus in the system. As a contrast, the annual total net accumulation of N, P, K in control (nature wild slope) was -9.59 kg hm^-2, suggesting an out flow of nutrients, N, P and K from the system. Meanwhile, simulation of N, P, K circulation in different compartments of the forest slope land and wild slope land within 0~10 years was described. The results indicate that N, P and K were in surplus in the broadleaf forest and conifer forest systems, and their accumulation in the ground parts of the plants was significant, but, in the soil compartment N was losing, and P and K were gaining. The results also show that nutrients in the soil compartment on the nature wild slope suffered slight loss.