Different flame retardant contents of polyurethane rigid foam (PRF) were prepared in this paper. Combustion performances of PRF were tested by cone calorimeter (CONE). Fire risk of PRF was evaluated based on Analytic Hierarchy Process (AHP). The evaluation results were compared with the traditional LOI results. It was found that the evaluation method based on AHP combined with CONE test results for evaluating fire hazard of thermal insulation material for exterior walls of buildings is more accurate and objective compared with the method of the traditional LOI.