Abstract: For the sake of studying isentropic compression of plane material irradiated by laser,based on the model of 1-D stress loading and entropy increase.The evolution of compression ratio,stress and entropy increase of plane material's Lagrangian points were computed with Lagrangian method and the existing experimental data.The simulation results are consistent with reported experimental results and show the basic characterization parameters, such as particle velocity, material specific heat,Hugoniot parameters and Griineisen coefficient.Quasic-isentropic compression can be judged with these parameters.