Abstract: The base of optical cavity is the major structure of a chemical laser. The dynamic characteristics analysis of the base is very important. Aimed at the practical base, modal simulation is done by two boundary conditions, the influential factors of dynamic characteristics are analyzed from the results. The first six modal parameters are obtained from the modal experiment. By comparing with the simulation, the shape characteristics are analyzed, the boundary condition of the bottom and the connection of corrugated tubes are also evaluated. The results are of benefit to the design and improvement of the chemical laser system. The results show that the connect stiffness is very low, and the constraint of corrugated tube does not change modal rules.