Based on the study of the duct overheat detection system of civil aircraft in existence, its shortage is pointed out. Therefore a modified overheat detection system is designed with heat-sensitive property material and combinational circuits, which owns the capabilities of alarm and location for the high-temperature and pneumatic duct overheat part. Some interrelated optimization methods are put forward as well. Also, the overheat detection experiment platform is built and the designed detection system is validated experimentally. The influences of the overheat length and the response time of internal air temperature on the system are conducted. The research results show that the response time of the detection system decreases with the increase of temperature of the internal air and the response time remains approximately constant when the temperature reaches a certain value. Meanwhile the response time of the detection system decreases with the increase of overheat length.