[Objective] To explore the adaptive mechanisms of soil microorganism and soil enzyme activity under grazing exclosure conditions in order to provide scientific basis for the recovery of degraded pasture.[Methods] Soil samples were collected from different soil layers (0-5 cm

5-10 cm and 10-20 cm) in Seriphidium transiliense desert under different exclosure years (0 a

3 a and 11 a) by zigzag sampling method. Then

the soil organic matter

catalase and urease activities

and the amount of soil microorganisms were measured by the conventional methods.[Results] The organic matter content in 0-10 cm soil layer increased with the increasing exclosure years

and the soil organic matter content of 11-year enclosure was 14.2% higher than that of the control. In the composition of microorganism

the largest amount was bacteria

followed by actinomycetes

and fungi was the least. The amount of bacteria and actinomycetes in 0-5 cm soil layer decreased and the amount of fungi increased with the increase of exclosure years

and compared with the control

the amount of bacteria and fungi of 11-year exclosure were decreased by 47.3% and 25.5%

respectively

while the amount of actinomycetes increased by 15.5%(p<0.05). There was no significant difference in the amount of bacteria in the 5-20 cm soil layer among different exclosure years

but the amount of fungi and actinomycetes increased with the increase of exclosure years. There was no significant difference on catalase activity in 0-20 cm soil layer among different exclosure years in S. transiliense desert. The urease activity in 0-10 cm soil layer increased with the increase of enclosure years

and that was decreased in 10-20 cm soil layer.[Conclusion] The long time enclosure is beneficial to the accumulation of soil organic matter

and can improve the amount of actinomycetes and urease activity in the topsoil.