In order to investigate the propagation characteristics of shock wave generated by thermobaric explosive,series experiments with thermobaric explosive of RDX/Al/AP/HTPB and the column mass of 400 g were carried out in an explosion chamber. Pressure histories were obtained by piezoelectric measurement system for the measurement points on the ground and in the air. The explosion process was simulated with AUTODYN software using JWL-Miller equation for detonation products. The parameters of JWL-Miller EOS were calibrated by experimental data. Results show that the error of peak pressure and action time between experiment and simulation are too small to be neglected. The Miller remainder can describe the after-burning features of thermobaric explosive reasonably. The simulated pressure distributions show that both normal reflection and oblique reflection occurred in the explosion chamber. Regular reflection and Mach reflection are two forms of oblique reflection. Normal reflection occurs at the ground projective point of the explosive charge. The peak pressure of reflected wave is 3.3 times higher than that of incident wave. Regular reflection occurs at where the incident angle is less than 40°,and the peak of reflected wave is about 2.5 times higher than that of incident wave. Mach reflection occurred at where the incident angle is more than 40°,and the peak of Mach wave is about 1.2-1.6 times higher than that of incident wave. There are regular reflections at side wall and dome. There is focus phenomenon at geometric symmetry axis. The peak overpressure of shock wave on the focus point is above 2200 kPa,and more than 4.3 times higher than that of incident wave. Reflection and focus of shock wave strengthen the overpressure in chamber.