Researches on material cycle of forest ecosystem have mainly focused on plants and soils, and few of them studied the role of soil fauna in the ecosystem. Most of the studies on soil fauna have been conducted in the laboratory environment or in artificially designed field to understand the role of biological factors in material cycle. This article is to study the dynamic characteristics of key nutrient elements of N、P and K in each component of the litter-soil fauna-soil system, and the functions of soil fauna in nutrient cycle by comparison of the differences of key nutrient elements in each component of the system. The study area is selected within the Liangshui National Natural Reserve of the Xiao Hinggan Mountains (128°47′8″-128°57′19″E, 47°6′49″- 47°16′10″ N). The study area has temperate continental monsoon climate with about -0.3℃annual mean temperature and 680 mm annual mean precipitation. The major soil type is mountainous dark brow forest soil. The characteristic vegetation type is mixed Pinus koraiensis and broad-leaved forest. We collected the forest litters including Tilia amurensis, Fraxinus mandshurica,Pinus koraiensis, Acer mono,Betula costata and mixed litter in different decomposition stages since the fall of the leaves in October of 2001, May, July and October of 2002. We also collected the soil samples in the humus horizon (0-5 cm) and soil horizon (5-20 cm), and soil macrofauna including earthworm, scolopendra and diplopod in May, July and October of 2002. We analyzed the contents of total N, P and K within the samples. We compared the differences of nutrient contents of the sampled litters in decomposition processes through variance analysis, and by the comparisons to reveal the role of soil macrofauna in the nutrient cycle among various components of the system. The results indicate that the dynamic characteristics of nutrient contents of litters in the decomposition processes are complicated. The changes of nutrient contents in broad-leaved litters are greater than that of coniferous from October 2001to October 2002. But the differences of nutrient content loss among various types of litters in decomposition processes are not significant. The nutrient contents of the humus horizon are higher than that of the soil horizon. The nutrient contents of the three sampled soil macrofauna are significantly different. The total N found in earthwormis the highest among the three soil macrofauna. Themaximum of total P was found in diplopod, and the maximum of total K was found in scolopendra. The dynamic changes of nutrient content in soils and soil fauna in the litters showed different trends. The soil macrofauna showed the role in accumulation of N and Pin the system,but the accumulation for K was rather weak. Soil fauna could accelerate the nutrient cycle rate in the litter-soil fauna-soil system by their metabolism. The dynamic of nutrient contents of vary litters through decomposition are complicated, which is possibly caused by the differences of various litters. The soil macrofauna could be considered as a transverter in the litter-soil fauna-soil system and play a significance role in nutrient cycle, especially in N and P cycle of the system.