Qinghai Sebei gas field is a shallow biogenetic gas field in the Quaternary formation, and its reservoirs are easilyprone to be deformed because of unconsolidated sandstones and poor lithologiesy, which results in obvious reduction of porosity and permeability during the process of pressure change. By overburden pressure experiments, porosity and permeability variation characteristics of Sebei unsolidated sandstone reservoirs isare analyzed. The relationship of porosity and effective stress is binomial. Dimensionless permeability reduces very quickly at the low pressure stage; however, it reduces slowly atat the high pressure stage. And at these two different stages, the relationships of permeability and effective stress are different, the former is exponential and the latter is the relationship of permeability and effective stress of is power. At the later period of gas field development, porosity will reduce by 10 percent, for gas reservoir pressure reduction and permeability will reduce to 0.1~0.6 times of original values and , whichit wwill influence gas production greatly-reduce gas well productivity by 47.1 percent. Simulation results show that, when rock deformation is considered during gas field development, the stable production period will reduce 3 years and recovery percent of reserves at the end of the stable production period and at 30 years will reduce respectively by 6.45 percent and 5.47 percent, respectively.