One electrical fire detector with anti-electromagnetic interference(anti-EMI) is designed in this paper, to solve its deficiency in electromagnetic compatibility (EMC). The design utilizes RN8209G power chip to acquire the signal, and communicates with the host by CAN bus. According to dissemination of electromagnetic interference, the design is divided into hardware and software. In order to raise anti-EMI capability, the hardware is improved in the power, communication, acquisition and PCB. On the software side, median filter and watchdog are adopted. Finally, the reliability of this design is validated in the professional EMC test laboratory.