Abstract: Take in Salah field in Algeria for example, numerical model has been established with the use of CGS-THCM coupled simulation program to simulate the changes of surface displacement caused by injected CO2 in different way. A method of combining Numerical simulation with monitoring data has been put forward to make comprehensive assessment of the CO2 escape problems during CO2 geological storage project. And the CO2 escape-surface displacement evaluation system has been established to assess whether CO2 escape and quantity size of the escaped CO2 during the CGS project. It is can be seen through simulation results: by the initial phase, smaller surface displacement be caused. And as time increased the surface displacement is more and more obvious. In addition, injection volume, injection pressure correspondingly cause large surface displacements.