In order to solve the issue, i.e. determining the weight of current coal mine safety comprehensive evaluation method in the subjective qualitative evaluation, this paper, according to the mining conditions, uses the rise of half normal distribution function to determine the extent of damage of each natural hazard in coal mines and the mine disaster prevention system, as the project weight of the coal mine safety comprehensive index evaluation method. Through calculation and comparative analysis, this paper confirms that the weight determination method can solve the current subjective arbitrariness and constant invariability when determining constant weight method. The weight can reflect the various dangerous source of the mines in the state of nature in a real time way. Thus, it provides a new method to determine the weight of the coal mine safety comprehensive index evaluation method.