Time reversal has the characteristics of spatiotemporal focusing and has potential applications in many field. The reversal system based on time reversal cavity (TRC) is an important reversal system. It can be used for pulse compression, beam forming, perturbation detection and so on. The TRC is usually an electrically large microwave chaotic cavity, and the propagation of electromagnetic wave in it has obvious multipath characteristics. That is, time dispersion characteristics. Therefore, in the process of time reversal, the TRC can compensate the phase of the reversal signal and reconstruct the initial signal, which can give time compression and spatial focusing at the initial position. To enhance the application of TRC, this paper studies the influence of cavity parameters on the reversal signal to noise ratio (SNR) based on the multipath channel model, focusing on the analysis of the influence of path attenuation, crosstalk and superposition. Moreover, it summarizes the main parameters and basic laws affecting the SNR.