Desert grey soil is one of the typical soil types in arid zone. Soils at Fu-Kang oasis and the surrounding desert were selected to represent the desert grey soil. The microbial community composition and microbial activities were compared between saline desert and oasis farmland at south periphery of Gurbantonggut desert. The eukaryote (fungi) and prokaryote (bacteria) contribution to microbial activity were determined with selective inhibition techniques applied to soils. The gradients of soil temperature (17-37 ℃) and moisture (8%-30%) were applied in treatments to understand the effects of temperature and moisture on soil microbial activities. Significant differences were found in microbial activities and community composition between desert and oasis. After the desert land was cultivated and became oasis, the number of bacteria increased, actinomyces decreased significantly, and fungi didn’t change that significant. There was a bacterial dominance, which was twice as much as fungal activities from April to July, in heterotrophic respiration at oasis field, but a fungal dominance at desert. Microbial activities in oasis field, including fungal and bacterial activities, were significantly higher than that in desert. Microbial activities both in oasis field and in desert were exponentially correlated with soil temperature, but the effect of temperature on the former was more significant. Temperature had significant effect on microbial activity in desert and oasis, but only for a given range of soil moisture. Meanwhile, the content of soil organic matter in desert was higher than that in oasis field, but had not resulted in high microbial activity in desert, which was likely caused by low soil moisture and high salt content. Namely, when desert became oasis after cultivation of the land, contrasting difference existed in soil moisture and salt content, which increased availability of soil organic carbon , and resulted in a significant difference in soil microbial composition and activities, and at the end, decreases of the soil carbon storage.