Abstract: In order to study the effect of crushing time to gas content measured value of seam,the high pressure adsorption device and crushing device were applied t 0 measure and test residual gas content of coal samples crushed after 0. 5,1. 0,1. 5,2. 0 and 2. 5 hours under adsorption equllibrium pressure of 1,2 and 3 MPa. The partic le diameters of coal samples were analyzed under different crushing time.The experiment results showed that when the crushing time was same,residual gas content of Co al crushed would be increased with increased adsorption equilibrium pressure. When the adsorption eqillbrium pressure was same,residual gas content of coal crushed W ould be increased with increased crushing time. After crushing time was over 1. 5 hours,residual gas content of coal crushed would be a constant value. When crushing tim e was over 1. 67 hours,the weight of coal sample with particles less than 0. 25 mm would be over 80%. Comprehensively With coal particle diameters distribution condition and residual gas content variation after coal crushed,rational crushing time of coal sample was 2 hours during gas content measuring process of seam.