Abstract: in order to reveal the difusion features of the gassy coal in the negative pressure environment the tifusion and desoption processes of the gassy coalwere sinulated underthe regative pressure environnent of 0,10.20,30 and 40 k Pa in the lab and a comparison anal sis was conducted on the gas descorption volum.desorption rat .dfifision rale and difuision ceicient unde a fferent negative prssure environment. The resuits showed that the gas desopton volume would be steadly increased with the environment pressure increased,the accumulated desorpton volume within 360 minutes would be increased by 37.45% in max and the negativeprssure would have a role to pronoe the gas desorption of the cal. Belore the frst 15 minutes.the negative pressure would have obvious infuences to the gas desorption rate especall ould have a max infuence to the gas desorption rate within the frst three minutes,the attenuation was about 60% and arer the frst15 minuesthe negative pressure would have less infuences to the desorption rate.Under the samecondtin of desopton balanced rssure.the gas di.fison coe Fice nt and th dtffusion c.eficient would all be increased with the negative pressure increased. The negative pressure increased would cause the dfision c eicient inreased and would be the main factor to promote the gas desorption.