Abstract: To measure gas content in coal seam efficiently and conveniently, a method using gas desorption ratio was presented in this paper. Results of the gas desorption experiments showed that gas diffusion coefficient values and their variations of a sample with different adsorption equilibrium pressures were similar, and the adsorption equilibrium pressure had tiny effect on gas desorption ratio in initial stage. Based on this, a method using the uniformity of gas desorption ratio in initial stage was established for gas content determination. The new method does not need to choose a desorption model and measure the residual gas content on ground. In the same place underground, the new method was compared with the gas content direct determination method and the result indicated that the new method could be used in engineering.