Abstract: To find the gas desorption law of mining pressure relief area,mathematical analysis and formula deduction of gas desorption law of mining pressure relief area are carried out,equivalent negative pressure drive effect and the theory maximum stress of gas desorption are found.And then combined with field test analysis,the gas desorption law is verified.The results showed that the coal stress variation of mining pressure relief area is the original impetus of gas desorption,and due to equivalent negative pressure drive effect the peak gas pressure shows little behind the peak coal stress,and peak value of gas pressure is less than the theory maximum.