Abstract: In order to study the gas extraction safety underground, based on the practical experience of coalbed methane development in typical mining area, the priority evaluation and the basic evaluation were confirmed combined with underground coalbed methane extraction technology and corresponding indicators, and the underground coalbed methane safety evaluation system was established. According to the evaluation of different stage, the different evaluation index was chosen, the general evaluation index consisted of gas press, gas content, desorption gas quantity, gas extraction rate, and the membership function was introduced to carry out uniform quantization for different evaluation indexes, a set of extraction standard was set up according to the corresponding specification and system. The different evaluation indicator was evaluated and analyzed after underground gas extraction with risk matrix and fuzzy mathematics, and the safety index was obtained from the safety function constructed by different indicator. In the light of the safety index value, the safety of underground gas extraction was divided into different level, the safety hierarchy was formed after gas extraction.