Biocrusts,as key participants in the carbon (C) cycle of drylands,can substantially influence dryland C emissions via respiration. However,the respiration rate (R_s) of biocrusts may differ significantly among different cover levels,and this remains poorly understood. In this study,we set up 5%,25%,50%,75%,and 100% cover on moss biocrusts developed in the aeolian sandy soil on the Chinese Loess Plateau,with bare soil as the control. Biocrust R_s were continuously monitored using a soil C flux system (Li-870). We measured soil properties (e.g.,soil temperature,moisture,and soil organic C). We further analyzed the differences in R_s and soil properties among different biocrust cover levels as well. Finally,we elucidated the mechanism underlying the differences in R_s among different biocrust cover levels through the construction of a structural equation model. Our results showed that: (i) the daily trends in R_s of different biocrust cover were generally consistent and their R_s were mainly influenced by rainfall. The daily variation of R_s of biocrusts with different cover levels showed a trend of increasing (7:00-13:00) and then decreasing (13:00-17:00),which ranged from 0.66 to 4.06 μmol m^-2 s^-1. The excitation effects following rainfall intensified as biocrust cover levels increased. (ii) R_s of biocrusts increased significantly with their cover. Compared with bare soil (1.09 μmol m^-2 s^-1),the increase in R_s were 28.2%,17.1%,9.3%,4.9%,and 0.6% for 100%,75%,50%,25%,and 5% biocrust cover,respectively. Meanwhile,the temperature sensitivity of R_s of higher biocrust cover was stronger. (iii) An increase in biocrust cover significantly enhanced R_s directly by elevating soil water content,moss biomass,and fines content (clay and silt particles). Also,an increase in biocrust cover positively affected soil organic C by increasing moss biomass and indirectly promoted R_s. In summary,the R_s of the biocrust responded significantly to the change of its cover,and the increase of the biocrust cover contributed significantly to the soil C emission rate by increasing the soil water content,improving the soil mechanical composition,and increasing the moss biomass. Consequently,changes in biocrust cover may occur under future climate change intensification which could lead to differences in C emission and should be taken into account when accurately estimating C emissions in the Loess Plateau of China.