Abstract: The mathematical model with threshold pressure gradient and injection-production ratio is constructed.The model is solved by numerical method.The characteristics of transient pressure curves are plotted and analyzed.The study shows that threshold pressure gradient and injection-production ratio have remarkable effect on characteristics of transient pressure.For the case of pressure dropdown test,pressure and its derivate type curves show the trend of rising when the injection-production ratio is less than 1.0,and the pressure drop of production also get increased;vice versa,pressure and its derivate type curves show the trend of declining when the injection-production ratio is higher than 1.0,and the pressure drop of production get reduced.For the case of pressure buildup test,the pressure buildup more highly as the threshold pressure gradient and injection-production ratio gets higher.Therefore,it is necessary to consider these factors in well test analysis.