Abstract: Due to the present situation of frequent fire accidents caused by the mobile power pack,fire risk based on the energy transfer theory and the fuzzy synthetic evaluation model was analyzed in the paper. Furthermore,fault tree analysis and the relative difference function are combined with the model to determine the weight values and memberships of evaluation factors. The evaluation results show that the risk level of fire accidents caused by the mobile power pack is between the safe and the more dangerous,which is agreed with the practical situation.