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Purpose Litter decomposition is a key process of nutrient cycling in terrestrial ecosystems, an important part of the global carbon budget, and deeply affected by global atmospheric nitrogen deposition. However, the effects of different forms of N addition on litter decomposition and nutrient release are unclear in a cold temperate coniferous forest in a subtropical Chinese plateau. Methods Three N sources (NH4)2SO4, NaNO3, and NH4NO3 were used in the gradient N deposition method. Each N source was divided into four treatments, from low to high, they were CK (control 0 kg N·hm− 2·a− 1), low N (low-N 5 kg N·hm− 2·a− 1), medium n (medium-N 15 kg N·hm− 2·a− 1), high N (high-30 kg N·hm− 2·a− 1), and each treatment repeated three times. Results After two years, the litter decomposition rates of low and medium ammonium nitrate treatments were the fastest as compared to the control, while high and low ammonium nitrate treatments were the slowest. Under the same nitrogen deposition conditions, the litter decomposition rates of low nitrogen treatments were higher than high nitrogen treatments. The order of litter decomposition rates was ammonium nitrate > ammonium sulfate > sodium nitrate. Nitrogen deposition decreased the amount of C in litter leaves but increased N and P levels slightly. Phosphorus changes over time were more complex than C and N over time. Conclusions These results showed that high nitrogen deposition in the future could increase litter decomposition rates and delay the nutrient release, which may be beneficial to improve soil carbon sequestration.