Abstract: In 4D seismic monitoring, the variation of reservoir features is mainly indecated by the changes of Lame constant, and eventually represented as velocity of layer and seismic response.Hence, Lame constant should be the most direct and sensitive indication for the variation of reservoir features under certain condition.In the paper, inversion methods of Lame constant are introduced and used actually in the inversion of 4D seismic monitoring data.The results show that it is feasible to use Lame constant inversion into 4D seismic monitoring.