Taking the Pinus rnassoniana pure forest and the Cyclobalanopsis glauca Oerst and Pinus massoniana mixed forest of the Ruxi River Basin in the Three Gorges Reservoir Region as test objects, an investigation was made of soil NH+4-N, NO3-N, SMBN and total nitrogen, and protease, catalase, urease and invertase activities of the 0-20 cm, 20-40 cm and 40-60 cm soil layers, so as to understand the difference between the two forest types. Total nitrogen of the three layers showed no significant differences between the two stands. Soil NH+4-N of the mixed forest in the 0-20 cm, 20-40 cm and 40-60 cm soil layers was 47.21, 47.69 and 43.83 mg/kg, significantly higher than in the pure forest by 13.7%, 24.8% and al. 5%, respective ly. Compared with the pure forest, the mixed forest increased soil NOa-N by 2.2% and 3.2%in the 20- 40 cm and 40-60 cm soil layers and SMBN by 77.4% and 60.4% in the 0-20 cm and 20-40 cm soil lay ers, respectively. Enzyme activities of protease, eatalase, urease and invertase of the three layers were sig nificantly higher in the mixed forest than in the pure forest. In conclusion, the ability to supply nitrogen to plants and to improve nitrogen cycle and enzyme activities was higher in the C. glauca Oerst and P. mas- soniana mixed forest than in the P. massoniana pure forest.