Based on the continuous CO2 flux observation with eddy covariance system conducted in the alpine shrub on the Qinghai-Tibet Plateau, the relationship between CO2 flux and precipitation was analyzed according to data of October and November in 2003, 2004 and 2005. The results shown that after individual rain events the large pulses of CO2 flux were observed over the alpine shrub ecosystem during October and November, and the increase exceeded normal variations under the former balance, evidently. The precipitation after longer dry period distinctly facilitate soil respiration, consequently, the CO2 flux over the alpine shrub markedly increased after the occurrence of precipitation during October and November.