Abstract: The burial depth of shale gas reservoirs is big in China, the conventional coring method is used commonly. Desorption measurement can determine the gas content more accuracy through the analysis of shale reservoir's conditions and pore structure. It can be found from the statistics that the relationship of cumulative desorbed gas content and desorption time of shale gas and coalbed methane is consistent, however the relationship of desorption rate and desorption time for them is quite different. The regression method for the calculation of lost gas can't be adopted blindly in shale gas desorption, and it is needed to select the stable gas desorption data carefully. It can be concluded from the analysis that the whole measurement process can be improved by calculating the lost gas stepwise based on third-stage desorption temperature. Meanwhile, for different formation pressure, lost time should be calculated based on the actual reservoir pressure, mud pressure and atmospheric pressure so that the lost gas content and shale gas content in conventional coring process can be calculated more accuracy.