The utility model relates to a temperature and humidity controller with self-checking capability, belonging to the technical field of temperature and humidity control equipment. The technical scheme is that the temperature and humidity controller with self-checking capability comprises a temperature and humidity sensor (1), a microprocessor (2), an outlet relay (3) and corollary equipment (4), which are connected in sequence; a voltage transducer (6) and a current transformer (5) are arranged between the outlet relay and the corollary equipment; and the outputs of the voltage transducer and the current transformer are connected with the microprocessor. In the utility model, as the current transformer and the voltage transducer are arranged in an output loop of the temperature and humidity controller, thorough self-checking function is provided to the temperature and humidity controller through the support of software design; by means of the self-checking function, the failure of an external power supply of the temperature and humidity controller, the failure of the temperature and humidity controller, the failure of the outlet relay of the temperature and humidity controller, the failure of external corollary equipment and the failure of a loop short circuit can be monitored; and thorough information about running condition and failure condition can be provided to maintenance personnel, so that the stable running is ensured and the failure check is convenient.