Abstract: Understanding the gaseous detonation reflection wave on concave surface is the basis for studying the propagation mechanism of detonation wave in annular pipeline. In this paper, the scale effect existing in the concave reflection process of gaseous detonation wave was experimentally investigated. The quantitative relationship between the triple-point trajectory and the critical wall angle with the geometric scale was obtained. The scale effect and two limits (freezing and equilibrium) similar to the detonation wedge Mach reflection were found. Further research revealed that the scale effect was highly dependent on two characteristic length scales, namely, cellular size λ and concave curvature radius of R. The proposed research may provide a theoretical reference for the design of combustion chamber for high-performance space propulsion system.