Abstract: The design of blast wave simulators for prototype or large-scale tests must carefully balance risk, cost, and performance. To address this challenge, a simulator driven by methane-air deflagration is developed in this study. Numerical models of methane-air deflagration in large-scale tubes were established by using the CFD software OpenFOAM and validated by comparing with testing data. Numerical simulations were conducted to analyze the effects of gas cloud length, venting conditions, and obstacle arrangement on overpressure loads. The mechanisms of blast wave and flame propagation in blast wave simulators were revealed and the experimental scheme was proposed. It is found that the numerical model can predict the overpressure time history and spatial distribution reasonably. Increasing the gas cloud volume and arranging obstacles near the ignition zone enhance deflagration intensity significantly. Side venting separates the pressure wave from the flame, thereby avoiding high-temperature distortion in the loading area. An optimized loading scheme was proposed for the developed blast wave simulator, employing four obstacles (1×50% + 3×25%, spaced 3 m apart) and variable gas cloud lengths (1.5 m - 6 m). The measured peak overpressure of blast wave simulator tests is in close agreement with the numerical predictions, with a deviation of less than 12%, good uniformity and high repeatability. The developed blast wave simulator is suitable for blast testing of components such as RC slabs.