Abstract: The paper introduced a intelligent low voltage integrated protector which was applied in coal mine underground,and elaborated the working principle and hardware and software design.The protector,with RS485 communication interface,utiliazed double CPU architecture of STM32F103 and STM32F101 based on Cortex-M3,which combined relay protection,intergrated test and control and remote data communication as one,and ensured the safety and reliable of underground power supply.