In order to solve the problems of poor anti-interference and low measurement accuracy of the existing insulation detection circuit, an insulation detection circuit is designed. The system uses STM32 microcontroller as the core control component, uses photoelectric quarantine and trap circuit to process the sampling signal, uses AD7192 sampling chip to complete the voltage acquisition, and then transmits the measured data to the microcontroller. The test results of the detection circuit show that the design improves the measurement accuracy and meets the detection requirements.