The electromagnetic wave time reversal technology using time reversal cavity (TRC) has potential applications in many aspects, such as pulse compression, power synthesis, perturbation detection, beamforming and so on. Microwave chaotic cavity with multi-path transmission characteristics is usually used in TRC. Based on diffraction theory, it can be proved that this kind of cavity has spatiotemporal focusing characteristics and can be used for pulse compression, but it cannot be used to analyze the reversal performance of the cavity. In order to get a suitable analysis method and guide the design of TRC, this paper analyzes the scattering, diffusion and attenuation characteristics of electromagnetic wave propagation and constructs the multipath channel model of TRC by the channel theory. Moreover, this paper studies the crosstalk characteristics between paths, and gives the generation mechanism of time sidelobe, time sidelobe shift and interference. In addition, according to the assumption of random plane wave, the distribution characteristics of spatial focal spot are analyzed, which is consistent with the diffraction theory. Moreover, The actual focal spot size is not only limited by the diffraction limit, but also related to the initial focal spot size. The theoretical analysis results are basically consistent with the experimental and numerical simulation results.