Abstract: To reveal the functions of arbuscular mycorrhizal (AM) fungi to beach plum and soil enzyme activities, we collected five samples with the rhizosphere of beach plum for each soil layer (0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm and 40-50 cm) from the Fujiabian hilly area in April, July and October 2009, respectively. We observed the AM mycorrhizal structure, determined the AM fungi infection rate, spore density, activities of phosphatase and urease, and the contents of available P and N in the soil, and analysed the relationship between AM fungi and soil enzymes. Results showed that AM fungi established a good symbiotic relationship with beach plum roots, and the symbioses were of vesicle-arbuscular structure. The 0-20 cm soil layer had the highest rate of AM infection and spore density in July and October, respectively, which decreased with the increase in soil depth. The AM fungi infection rate showed significant positive correlation with the activities of acid phosphatase, neutral phosphatase and alkaline phosphatase, but no correlation with urease in soil. The AM fungi spore density demonstrated significant positive correlation with alkaline phosphatase and urease in soil. There was a significant positive correlation between spore density and available P (or N), but no correlation between AM fungi infection rate and available N. Spore density showed no correlation with AM fungi infection rate. The AM fungi infection rate and spore density had obvious spatial and temporal distribution, and were related closely to the activity of soil enzymes. With AM mycorrhiza, beach plum could grow well on poor hilly mountains.