In order to study the equation of state (EOS) of the detonation products of RDX-based PBX at small scale,cylinder tests were carried out to identify the power of RDX-based PBX with density of 1.65 g·cm^-3 . The copper tubes with diameter in 10 mm and 25 mm were used. The scale of the wall expansion and the velocity were measured. The cylinder tests were numerically simulated by nonlinear finite element dynamic program Ansys/Ls-Dyna. The parameters of the JWL EOS for RDX-based PBX were calculated and corrected according to the numerical simulation results.