Abstract: In order to accurately calculate gas loss of western Henan “three soft” coal seam during sampling, the gas desorption process simulation test of coal particles collected in Gaocheng Mine is made under conditions of temperature 30 ℃ and pressure 0.6 MPa. According to the experimental results, the fitting effects by Barrer Formula and Ustinov formula were analyzed relatively in the early of desorption process. We comparatively analyze computative loss error of t^0.5 and power function, and choose the appropriate predicting gas loss method. Research shows that t^0.5 function is more in line with gas early desorption laws of coal particle. We confirm that the reasonable desorption time of computative loss error is 6~9 min, and loss projection correction coefficient is 1.117 8.