Abstract: Based on full study on the original analog temperature controller of ventilation system in nuclear power plant, for the interface definition fixation, parameters preset as well as multiple output combination of the temperature controller circuit, a digital temperature circuit based on the front-end input conditioning module + multi channel ADC+STM32 architecture is proposed. The hardware structure and software process are described in details. The sampling data processing, phase-cut voltage output as well as control principle are focused, and some part of software program is presented. The experimental results show that the temperature controller can stably and reliably control the temperature of ventilation system and display digital parameters, and it can completely replace and upgrade the original analog controller.