To reduce the losses caused by fire disaster of underground commercial street, Using Interval Analytic Hierarchy Process (IAHP) to assess the risk of underground commercial street fire disaster. Applying modified Delphi method from 4 aspects such as :fire resistance property, fire-fighting capability, fire management and evacuation capability to build third-level safety evaluation index system of underground mall fire disaster. Adopting IEM to calculate the weight value of each index, and conduct the rank of weight value under the overall objective. To confirm the reliability of evaluation model, Took west Xiangtan underground commercial street fire disaster system as an example for calculation, the result of evaluation showed that the main risk factors of the underground commercial street of west Xiangtan fire disaster are divided into three aspects: ability of escaping, fire fighting propaganda, fire load of fire disaster.AS a result, evaluation conclusion correspond with the actual situation.