Abstract: During the process of determination of the lower limits of gas reservoir physical properties with conventional productivity simulation method, the well producing pressure differential is approximately set as the experimental pressure differential for productivity simulation. However, the core size and single well control area are quite different, resulting in the fluid flow rate at core outlet?end not equal to that at wellbore end, leading to relatively large error in predicted results. Therefore, the conventional productivity simulation method should be improved. Similarity transformation of pressure differential is added before production similarity conversion, based on which experimental pressure differential is set to guarantee the equal fluid flow rate. The improved productivity simulation method is used to determine the lower limits of reservoir physical properties in Moxi district of An’yue gas field. The result shows that the lower limits of porosity and permeability determined by the improved productivity simulation method are 2.74% and 0.015 mD, respectively when the producing pressure differential is 6 MPa and the net pay thickness is 40 m in gas wells; while the lower limits of porosity and permeability determined by the conventional productivity simulation method are 2.42% and 0.011 mD, respectively, which is slightly lower than those determined by the improved method. The lower limits of reservoir physical properties determined by the improved productivity simulation method are more accurate.