Abstract: Polythene film used as confinement plays an important role in flammable cloud explosion.Experiments of C₂H₂/air cloud explosion were performed at 7.8% ethyne concentration.Polythene film with different thicknesses(0.02, 0.04 mm and 0.06 mm) and different layers (1—4) were adopted in the experiments.The results showed that, the maximum overpressure was 2.410 kPa in the explosion of hemisphere cloud with radius 0.5 m, while, as the thickness of film was 0.06 mm,the maximum overpressure reached 3.642 kPa.When 4 layers of film were adopted, the maximum overpressure reached 13.125 kPa.A theoretical model, considering the influences of intensity and layers of polythene film on explosion, was established and solved by SIMPLE algorithm.Compared with the test data, the maximum and average relative deviations of calculation results were 14.8% and 4.73% respectively.The results are of great significance on forecasting gas cloud explosion with weak confinements.