Cajanus cajan is one of the most important plants that plays an irreplaceable role in ecological environment protection. In order to provide scientific utilization and management about it, we took the sample plot in Yuanmou dry-hot Region and studied the nutrient cycling and the efficiency of nutrient utilization of the C cajan 2-year old plantation in the different planting densities. The results showed: the nutrient cycling was different among the different planting density of C. cajan, but the efficiency of nutrient utilization was same among the different planting densities .The quantity of annual nutrient absorption of 0.8×0.8m²,1.0×0.8m² and 1.0×1.0m² planting density was 1499.64,1326.26 and 1046.01kg/(hm²•a) respectively, and the annual adsorption amount of each element from soil was different , Ca is most , then followed by N and K, Mg, P, Fe and Cu . The absorption of these elements trended to increase with the higher planting densities, the return was 476.30，729.95 and 518.98 kg/(hm²•a) respectively. The retention was 753.34,596.3 and 527.07 kg/(hm²•a) respectively; the cycling ration of macronutrient was 0.49、0.55 and 0.49 and the cycling rate of micronutrient was 0.79,0.83 and 0.80 respectively. The results also showed that the planting density of 1.0×0.8m² was more effective in using the nutrient cycling and the nutrient efficiency utilization and keeping soil of sustainable development. Compared with those of Pine,Black locust Castanca mollissima Blume and Castanopsis, the nutrient utilization efficiency of C. cajan was evidently lower , particularly for N and Ca.