Abstract: Aiming at the need for real-time monitoring of resistance spot welding process information, a portable resistance spot welding monitor with STM32F405 as the core was designed, which is different from the monitoring scheme of the existing acquisition system with host computer. The monitor can realize multi-information collection of spot welding process, real-time curve display, and process monitoring based on envelope curve. The test results show that the monitor has high detection accuracy, the maximum error of all detected process information is 1.0%. For spot welding of enameled wire,by monitoring the envelope curves of pressure and resistance signals, it is practicable to effectively judge the welding abnormality of enameled wire disengaged from pad. The monitor has complete functions, and can be used in multiple production environment, and satisfies the requirements of real-time data collection and analysis.