Litter decomposition is an essential component of the nutrient balance and material cycling in Pinus massoniana plantations. Forest gap size could play an important role in litter decomposition due to its effects on the microenvironment. To evaluate the effects of forest gap size on leaf litter mass loss and nutrient release of four native species (Toona ciliata, Phoebe zhennan, Cinnamomum camphora, Pinus massoniana), a field experiment consisting of seven gap sizes (i.e., G1:100 m², G2:225 m², G3:400 m², G4:625 m², G5:900 m², G6:1225m², and G7:1600 m²) was established in 2013. The results showed that:1) Forest gap size significantly affected leaf litter mass loss of C. camphora, but not the mass loss of the other three species. The litter nutrient release rate at the gap center for T. ciliata (N, P), P. zhennan (N, P), C. camphora (N, P, K) and P. massoniana (P, K) were significantly influenced by forest gap size. Furthermore, leaf litter mass loss rate, and N and P release rates were significantly higher in small and medium sized gaps (G1-G4) than in large gaps (G5-G7) (P < 0.05). However, litter K release rates were significantly lower in small and medium sized gaps (G1-G4) than in the larger gaps (P < 0.05). 2) The leaf litter collection location in the forest gaps influenced the litter K release rate of T. ciliata, P. zhennan, and P. massoniana. The K release rate of T. ciliata and P. zhennan litter at the gap centers were significantly higher than those at the gap edges (P < 0.05). In contrast, P release rates of C. camphora litter and K release rates of P. massoniana litter at the gap center were significantly lower than rates at the gap edges (P < 0.05). 3) Litter mass loss and nutrient release rates of T. ciliata were the highest among the four species. According to the fitting equation, the 50% and 95% decomposition times for T. ciliata were 5.29 and 23.14 months, respectively. Overall, forest gap size and litter sampling location in the gaps significantly affected litter mass loss and nutrient release. However, the extent of these effects and dynamic changes depended on the initial litter quality. These results can be beneficial for the scientific management of P. Massoniana plantations in low mountainous and hilly areas of subtropical zones.