Abstract: The porosity of reservoir rocks is one of the most essential and important formation parametersin pool development. As we know,during the development of reservoirs,the formation pressure is reducing,that is to say,the effective overlying pressure is increasing. Porosity is stronger effected by porositystress sensibility. Study porosity stress sensibility has important meanings to reservoir development. Thispaper presented a porosity stress sensibility model in theory by means of porosity volumetric strain ,brought forward a parameter named porosity stress sensibility coefficient,then took it as a method to evaluate porosity stress sensibility. This parameter is based on the change of pore compression coefficient,soit can describe porosity stress sensibility more accurately than using pore compression coefficient. Combining theoretical rules with the experiment,the theory was proved to be true by the experiment of porositystress sensibility under the simulating formation situation.