Abstract: At present, thermal simulation experiments on accumulating rules of shale gas mainly follow the conventional method, which uses powder samples as the simulation object and does not define the shale gas as retention gas. Moreover, the powder samples after simulation cannot be observed by Scanning Electron Microscopy (SEM), and thus the evolution rules of pore structure cannot be determined. A new thermal simulation experiment method for shale gas, which uses a quartz glass tube to package the sample, and the linear regression method to analysis the data has been established. The changes of gas content and microscopic pore characteristics in shale during different phases of evolution (Ro range of 0.596%-2.143%) were studied. Results show that the contents of vent gas and desorbed gas in mudstone and oil shale increase obviously in high-mature stage with temperature higher than 400℃. Combined with SEM analysis, it can be inferred that this trend may be caused by the increasing of inorganic pores and gas generated from organic matter. This method can provide change information of shale gas contents and pore characteristics during the thermal transformation, which is more suitable for the study on the shale gas exploration and development.