Abstract: In order to determine the critical value of coal and gas outburst forecast indicators, accurately predict the outburst of the heading face, according to the fuzzy set theory and fuzzy statistical data fitting, the paper obtains membership function curve of forecast indicators, and studies membership of forecast indicators. The study shows that the critical value of the coal cuttings desorption index(△h₂) of C₅ coal seam in Guizhou Rongguang Company is 180 Pa.