Abstract: The 30-year-old biological soil crusts dominated by mosses (hereafter moss crusts) and corresponding uncrusted soil (hereafter no crust) were sampled on loess soil and aeolian soil at 0-12 cm depth on the Loess Plateau of China. Afterwards, the hydrolase activities of the samples were measured, and their correlations with soil physicochemical properties were analyzed. Compared with no crust, the activities of urease, alkaline phosphatase, invertase, and protease of the moss crusts were 2.4, 7.6, 20.7, 2.4 times higher on loess soil, respectively; while they were 3.5, 22.2, 22.3, 2.0 times higher on aeolian soil, respectively. Compared with no crust, the soil water content of the moss crusts was decreased by 6.5% and 0.8% on loess soil and aeolian soil, and the soil temperature of the moss crusts was decreased by 0.8 and 2.5 ℃, respectively; the contents of soil organic matter, alkali-hydrolyzable nitrogen, and available phosphorus of the moss crusts were 2.5, 2.9 and 3.6 times higher on the loess soil, and they were 3.6, 3.0 and 6.6 times higher on the aeolian soil, respectively. The soil hydrolase activities were positively correlated with the soil nutrient content and negatively correlated with the soil water content. Soil temperature was positively correlated with the urease activity and negatively correlated with the protease activity. The moss crusts significantly improved soil nutrients and fertility through increasing soil enzyme activities on the Loess Plateau of China, and these effects were reasonably attributed to the moderate soil water content and temperature regulated by the moss crusts.