Abstract: The trees growth, soil physical and chemical characters and enzyme activities under mixed forest of Chinese fir and poplar(Populus deltoids cv. ’Lux’) and pure stand of Chinese fir were analyzed. The results indicated that trees growth, soil structural property and soil nutrients in mixed forest were better than that in the pure one, and the soil enzyme activities were enhanced. Thus this model was an effective measure to prevent decrease of the soil fertility of forest land for the continuously planted Chinese fir, and it is worth planting in the coastal areas in the northern Jiangsu province.