Based on the effect of depressurizationrapid depressurization property of dual power drilling was investigated.The realizing condition of dual power drilling and the principal of helical coal breaking were analyzed theoretically.Adopting the FLAC 3D softwarethe model was established to study the rules of stress revolution around the relaxed slot.Besidesthe industrial experiment was conducted.It indicates that the advanced free surface can eliminate the confining pressure and lower the resistanceincreasing the drilling rate significantly.The relaxed slot boost the coal mass rheology occurmaking the concentration stress move deepergas potential energy releasedthe coal strength enhanced and thus the fatality of outburst removed.Industrial experiment shows that after adopting this measurethe perturbation range enlarges forty times and the depressurization radius four times.The efficiency of gas drainage improves substantiallythe fatality of outburst in control region is removed and tunneling progress raises two times.