With the development of society, more and more infrastructure are built in the underground space. So an effective method of safety assessment can provide support to the normal operation of the underground space. This paper investigates the five kinds of underground space, including commercial, culture and entertainment, fitness, hotel, dining and garage. According to the real situation of underground space in Beijing, firstly, the safety factors are identified. Then, the safety evaluation index system is established with the experts' opinions, and the index weights are determined using AHP. At last, fuzzy theory is referred to the safety evaluation and a fuzzy comprehensive evaluation model is built. Then the method is verified by an example.