Abstract: In order to analyze the influence of the film on the test results of the unconfined gas deflagration, a refined finite volume model was built up based on the deflagration test with hydrogen-air mixture of 10 m radius by use of the computational fluid dynamic software AutoReaGas. The comparison between the numerical results and the test data shows that, the model is able to predict the influence of the film on the gas deflagration, and the ruptured overpressure of the film in the test is about 0.5 kPa~3 kPa. Furthermore, the influence of the film on the deflagration overpressure of the hydrogen-air, acetylene-air and methane-air mixtures with the volumes of 1 m³, 8 m³, 125 m³ and 1000 m³ were analyzed by AutoReaGas. It is shown that the influence of the film on the deflagration overpressure decreases with the increasing of the gas volume, burning velocity and distance. The suggestion on the choice of the film in the gas explosion tests was also given.