The purpose of this study was to investigate the changes in soil microbial biomass and enzymes activities during the decaying of Salix psammophila sand barriers. The sand barriers which had been laid for ten years were used as the research object. The research methods included field in-situ sampling and laboratory tests. Combined with RDA data sequencing analysis, the main environmental factors affecting soil microbial biomass and enzymes activities were revealed. The results showed that the values of C:N and C:P in soil increased with the increase of laying years. The C:N value in 10 years was 16.14 times of that in one year, while the N/P decreased by 83.96% after 10 years. The soil MBC, MBN and MBP increased firstly and then decreased with the decaying, and reached the maximum value in the 7th year, which was 2.67, 2.18 and 1.43 times that in the 1st year, respectively. With the increase of decaying years, the activity of soil alkaline phosphatase increased first and then decreased. It peaked in the 6th year and showed a significant difference (P<0.05), but the activities of urease and sucrose in one year were significantly higher than those in others (P<0.05). The RDA analysis showed that the sequences of the major soil physical and chemical factors affecting soil microbial biomass and enzymes activities were as follows:available potassium>water content>C:N ratio>alkaline hydrolysable nitrogen>pH>available phosphorus>N:P ratio>C:P ratio. The main driving factors were soil available potassium and water content. The results of this study could provide an important theoretical basis for the study on soil carbon, nitrogen and phosphorus cycling in the desert ecosystem.