The canopies in evergreen coniferous plantations are often composed of various-aged needles. Plantation management, such as thinning, produced abundant harvest residue, including needles with different needle ages. However, little attention was paid to the effect of needle age on decomposition, although the needle chemical properties varied substantially with leaf ages. A field experiment was conducted for 3 years to investigate the decomposition of harvest residue needles at different needle ages, and determine the main controlling factors in different stages of decomposition in a Chinese fir plantation. We found that the initial decomposition rate varied 5-fold among different needle ages in a Chinese fir plantation. Litter quality controlled the overall litter decomposition rate, especially the initial decomposition rate. Needle nitrogen content was positively correlated to decomposition rate during the early stage of decomposition. However, it was negatively correlated to decomposition rate during the later stage of decomposition. The contents of needle tannins increased the asymptotic mass remaining (A, proportion of mass remaining at which decomposition approaches zero, i.e., the fraction of slowly decomposing litter). We also found that the initial litter decomposition rates in soil fauna presence were significantly higher than those in soil fauna absence across different needle ages. Moreover, the effect of soil fauna on initial litter decomposition is independent of needle quality. Our results suggest that needle age and plant secondary metabolites should be considered to understand the response of litter decomposition and nutrient cycling to management practices, such as thinning, in conifer plantations.