The complete degradation of litter results from the combined enzyme activities in litter layer and soil layer, and their improvement is helpful to organic matter decomposition and nutrient release. Litter decomposition and the seasonal dynamic of soil-litter layer enzyme activities were studied on 30-year-old P. massoniana forest in Three Gorges Reservoir Area. The results showed that the remaining mass was 59.80% after 540 days decomposition. The decomposition rate was relatively fast during the decomposition 0-180 d, and relatively slow during 180-270 d. The period of 50% mass loss and 95% mass loss was 2.11 a and 9.15 a, respectively. The litter layer enzyme activities exhibited a remarkable seasonal dynamics, with the lowest enzyme activity occurring in November and the highest in March for oxidoreductase activity. Polyphenoloxidase activity and peroxidase activity of litter layer in March were 4.60 times and 6.07 times as high as those in November, respectively, while the dynamic of hydrolase activity in litter layer was irregular variation. The seasonal dynamics of soil layer peroxidase activity was remarkable with the lowest value occurring in November, and the highest in June. Polyphenoloxidase activity was the highest in September. The seasonal dynamics of soil layer hydrolase activity was irregular variation, the seasonal dynamical of soil urease activity was not significant (P>0.05), while the cellulose activity and sucrase activity was significant (P<0.05) with the sequence of September < June < November for sucrase activity, and the sequence of November < September < June for cellulose activity. Soil enzyme activity in the vertical direction was decreased gradually with soil depth except peroxidase activity. There was a notable difference in enzyme activity between litter layer and soil layer, and the difference in hydrolase activity was greater than in oxidoreductase activity. Litter layer urease activity, cellulase activity and sucrase activity were 6.33 times, 3.24 times, 10.29 times as high as those in 0-5 cm soil layer in November; 68.14 times, 16.16 times, 24.81 times in June, and 25.07 times, 31.88 times, 29.20 times in September, respectively. Litter polyphenoloxidase activity in November, June and September were 1.76 times, 1.45 times and 2.07 times as high as those in 0-5 cm soil layer, and the corresponding value were 0.40 times, 0.64 times and 0.56 times for peroxidase activity, respectively. There was a close relationship between litter-soil enzyme activities. Litter decomposition rate was significantly correlated in S-shaped curve with oxidereductase activity both in litter and soil layer, probably because oxidoreductase activity dynamic is complex and influenced by soil pH value, nutrient content, soil layer distribution and so on. There were significant quadratic function (P<0.01) between litter decomposition rate and hydrolase activity in litter layer, while litter decomposition rate was significantly linearly related (P<0.01) to the hydrolase in soil layer. Litter quality could change the enzyme activity in litter and soil layer, in return, enzyme activity could affect litter decomposition rate. Therefore, the difference of enzyme activity between litter and soil layer is related with litter decomposition stage and the different sensitivity of the common impact factors including litter quality, soil temperature, water content and soil nutrients. The interactions of litter-soil layer enzyme activity influence material circulation and nutrient cycling process of forest ecosystem.