This paper introduces fire supervisory system design based on embedded system using by ARM9. Embedded technology and field bus technology are used for the system design. The system can realize detecting on-line. Showing uninterruptedly the information for fire monitory point of the building, the working current for electricity lines, the leakage current, as well as environmental temperature parameters e.g., through the LCD panel. Through this system The fire information of the building and the electrical wiring or the change, fault and abnormal condition for fire danger parameters of the equipment can be mastered at any time, and the hidden fire danger can be found in time, eliminating the hidden fire danger through the alarm and terminal linkage device.