【Objective】Climate change triggers variation of soil net primary productivity, which are likely to affect litter input to forest soil. Litter is an important source of nutrients for plants and soil microorganisms in forest ecosystems and may also alter stocks and cycling of soil carbon (C) and nitrogen (N). However, so far little has been found in the literature about responses of soil C and N to litter input in subtropical forests. This study aims to understand how soil C and N respond to increased litter input in a Chinses fir plantation in South China, caused by climate change. 【Method】In this study, a four-year field experiment, designed to have two plot, Plot A with litter kept on the soil and Plot B with litter removed, was carried out in a Chinese fir plantation in South China. Soil samples were collected from the plots at the end of the experiment and analyzed for soil C and N and their isotopes (δ¹³C, δ¹⁵N), enzyme activity microbial biomass C and N (MBC, MBN), as well as N-acquiring enzymes. 【Result】Results show that Plot A significantly increased activity of soil N-acquiring enzyme activity (β-N-acetylglucosaminidase) and hence accelerated decomposition of soil organic matter. Therefore it was found that litter triggered decline of soil ammonium, nitrate N and DON, but barely affected soil MBC and MBN, which is probably because litter intensified the competition of microbes with plants for soil N, so soil microbe released more N-acquiring enzyme to meet their demand for N. In Plot A phenol oxidase and peroxidase increased in activity,while in Plot B they decreased in activity, which indicates that soil microbes tend to decompose Chinese fir litter rather than soil organic matter as energy to acquire N. In Plot A soil organic C and dissolvable organic C did not vary much, which indicates that litter does not have much impact on carbon in the soil. Litter did not have much impact on soil δ¹³C either, but did, by significantly increasing soil δ15N. Soil δ¹⁵N is an indicator of openness of soil N system. The higher the soil δ¹⁵N, the more open the soil N system, the more likely the occurrence of N loss, which indicates that litter accelerates soil N mineralization and loss. Besides, it was also found that in Plot B β-glucosidase and cellulolytic enzyme declined in activity, which indicates that litter removal may downregulate soil C recycling rate. 【Conclusion】Based on the findings of the experiment, it could be concluded that 1) litter significantly affects soil N, but not soil C, which indicates that soil N is more sensitive to changes in litter input than soil C; 2) Litter may alter the soil microbial environment of the Chinese fir plantation and enhance root growth and N uptake of the plant, thus leading to intensified competition between soil microbes and plants for soil N and decline of soil N in content; 3) As Chinese fir litter is high in C/N, soil microbes need to excrete more soil phenol oxidase and peroxidase activity to decompose fresh litter for energy to compete for soil N. Therefore, climate changes cause variation of litter production in Chinese fir forest, which in turn produces different impacts on recycling of soil C and N, thus disturbing balance of soil C and N in subtropical coniferous forests.