The invention discloses a comprehensive performance testing device for an oxyhydrogen composite catalyst and an application method thereof. The comprehensive performance testing device comprises a reaction tank, a test tooling, a measuring system, a data acquisition system, a multipath gas introduction control system and auxiliary testing equipment, wherein the test tooling is mounted in the reaction tank and is used for placing a catalytic board; the measuring system is mounted on the reaction tank and is used for detecting the concentration, the temperature, the pressure and other parameters of gas in the reaction tank; the data acquisition system is connected with the measuring system; the multipath gas introduction control system provides exogenous gas required by the test; the auxiliary testing equipment is connected with the reaction tank. According to the comprehensive performance testing device disclosed by the invention, the design is ingenious; the complex environment of a nuclear power station under the working condition of serious accidents is simulated by an oxyhydrogen composite catalytic board through special equipment, so that environment parameters of the catalyst can be adjusted at any time; all required data is accurately detected by the measuring system and various performance tests of the catalyst are realized; the transfer and the assembly of the catalytic board are eliminated, so that great human and material resources are saved; the time and the labor are saved; the comprehensive performance testing device is convenient and safe in use, simple and quick in debugging and comprehensive and sufficient in detection, and has high popularization and application values in the field.