In Consideration of the influence of the bottomhole storage and the skin effect, the mathematical model of multilayer composite reservoir is established under the different outer boundary (infinity, closed, constant pressure) conditions. By using the Laplace transform, the exact solution of multilayer composite reservoir is obtained in the corresponding Laplace space. By analysis, the similar structure of Laplace space solution of reservoir pressure for multilayer composite reservoir is obtained in the inside and outside region. The similar structure of solution has a farreaching influence on analyzing inherent law of solution, compiling of well test analysis software and researching the laws of the reservoir seepage.