Abstract: Acid treatment is an important measure to improve production and injection for producer and injector, and pressure transient well test is one of methods for evaluating effects of acid treatment. This paper studies pressure transient behavior of a well when porosity and permeability changed with acid treatment. The well test model is established by considering the exponential change of the porosity and permeability with radial distance. The wellbore pressure typical curves have been calculated by FEM method and their characteristics have been analyzed. The case analysis shows that the application of the well test model given by this paper has a satisfied result, and give a method for evaluating acid treatment more accurately.