Water is the major driver of ecosystem functions and processes in semiarid and arid regions, Water availability is directly linked to precipitation, and variation in the productivity of desert shrublands and grasslands is well known to correspond to seasonal and inter-annual rainfall patterns. In such water-limited ecosystems, pulsed precipitation directly control the below ground processes through a series of soil drying and rewetting cycles. Precipitation events are infrequent and discrete in semiarid and arid region. Global circulation models predict a shift in precipitation patterns to growing season rainfall events that are larger in size but fewer in number. This "repackaging" of rainfall into large events with long intervening dry intervals could be particularly important in semi-arid grasslands because it is in marked contrast to the frequent but small events that have historically defined this ecosystem. In arid ecosystems, soil microbes respond to very limited precipitation events. However, larger precipitation pulses are required by vascular plants for photosynthetic activities. Biological soil crusts are an integral part of the soil system in arid regions worldwide, stabilizing soil surfaces and aiding vascular plant establishment. They are also significant sources of ecosystem nitrogen and carbon. Biological soil crusts can take advantage of limited moisture in the air for photosynthesis, and carbon exchange involving biological soil crusts is an important component of soil carbon fluxes in arid areas. In the Gurbantunggut Desert, about 28.7% of the area is covered by biological soil crusts dominated by lichen. In this paper, to discuss the effect of biological soil crusts on apparent soil carbon fluxes under different amounts of precipitation, CO₂ fluxs in soil covered with moss-lichen crusts and in crust-removed soil from the central Gurbantunggut Desert was measured by infrared gas analyzer after addition of simulated amounts of precipitation of 0 mm, 2 mm, 5 mm, and 15 mm. The results show that: (1)the release of CO₂ from biologically crusted soil was trigged by precipitation, with the accumulated carbon eflux under 2 mm, 5 mm, and 15 mm of simulated precipitation being 151.48%, 274.97%, and 306.44%, respectively, of that of the control. As time elapsed after rainfall, the carbon flux decreased until it reached the value equivalent to that before precipitation was applied; (2)Biologically crusted soil and soil with crusts removed had different responses to precipitation with the carbon flux being significantly different between biologically crusted soil and bare soil after addition of 2 mm of simulated water. Biologically crusted soil emitted more carbon than bare soil under 0mm and 15 mm of simulated precipitation, although the differences were not significant; (3)A large release of activated carbon after an initial simulated precipitation event was followed by a decline in the soil carbon efflux after further simulated successive rainfall events, with the decline in the flux release rate from bare soil being positively correlated with rainfall intensity. The study shows that the effect of biological soil crusts and successive rainfall events should be taken into consideration when discussing the response of soil carbon exchange in arid lands to simulated rainfall.