Abstract: Six years of continuous researches were conducted on the soil moisture, nutrients, physical and chemical properties,structure and benefits of mixed forest of Pinus tabulaeformis and Robinia pseudoacacia in the dry valley of the upper Minjiang River. The main results were as follows:(1) the average soil moisture between 0 and 40 cm in mixed forest increased by 0.91 g·kg^-1 and 0.55 g·kg^-1 than that in Pinus tabulaeformis and Robinia pseudoacacia pure forest respectively; (2) The soil bulk density in mixed forest of 18 years old decreased by 0.13 g·kg^-1 and 0.10 g·kg^-1 than that in Pinus tabulaeformis and Robinia pseudoacacia pure forest respectively; (3) Soil organic matter, soil available nitrogen, soil phosphorus and soil CEC content in mixed forest increased by 0.54 mg·kg^-1~1.48 mg·kg^-1,6.4 mg·kg^-1~19.4 mg·kg^-1,0.36 mg·kg^-1~1.37 mg·kg^-1 and 0.23 mg·100 g^-1~0.85mg·100 g^-1 than those in pure forest respectively; calcium carbonate content of the soil and soil available K decreased by 0.43 mg·kg^-1~1.09mg·kg^-1 and 6.90 mg·kg^-1~23.90 mg·kg^-1 than those in pure forest respectively. (4) The canopy area,canopy thickness and canopy moisture retention rate of the mixed forest increased by 47.83%~78.95%,40.63%~73.08%,6.15%~8.32% than those of the pure forest respectively. The litter saturated water was 1.62 times~4.22 times than that of pure forest; (5) The height and diameter in the mixed forest increased 24.7% and 27.35% respectively as compared with the pure forest. The profit of mixed forest was 7.12 times than that of pure forest.