Abstract: Through hypothesis and formula derivation, a reasonable method was proposed to determine outburst-preventing extraction volume of outburst coal. Formula derivation result indicated that outburst-preventing extraction volume of outburst coal equal the pure flow of drainage which was needed to make the coal quantity of designed capacity to reach standard through pre-drainage in a year multiply working face area uneven coefficient. The outburst-preventing extraction volume which was determined by above method has important significance on choosing reasonable gas drainage system and equipment for coal mine.