For the question of gas exceeding limit on the coal face, the gas desorption experimental measuring device under external solution invasion is used; and the device is the result of independent research and development. Under the conditions of external solution invasion and no external solution invasion, gas desorption comparative experiments are carried out, the experiment data and curve of gas desorption are obtained, and the influence of external solution invasion upon gas desorption is analyzed. The results show that whether or not there is the external solution invasion, the higher gas pressure of coal with gas is, the larger gas natural desorption quantity is, and gas desorption is mainly concentrated on first 1h; after external solution invades, water lock effect on the coal with gas could be produced, therefore gas desorption quantity is reduced and gas release speed is slow down. Preventing gas from exceeding limit on a coal face by using water lock effect is feasible, it could be implemented through two solutions, that is, coal bed infuse solution and spraying permeable agent solution during the coal mining.