Abstract: In order to determine the critical value of the inspection index(gas pressure p and gas content W)of regional gas pre－drainage effect in three－soft unstable outburst coal seams in west Henan coal filed，the corresponding relationship between gas desorption index Δh₂and gas pressure p was constructed by establishing a laboratory experiment system，based on this relationship and the gas pressure p and gas content W which were measured in the region of gas outburst and gas dynamic phenomena occurrence，it was comprehensively deternimed that the critical value of the inspection index p and W of regional gas pre－drainage effect was respectively 0．4 MPa and 5．0 m³/t，which were then verified by the actual mining．These critical values are different from some existing regulations，and the research method and results can be used for reference to similar coal seams．