The invention provides a fire extinguishing plug for cable trench internal fire early warning and automatic alarm. The fire extinguishing plug is characterized by comprising a data display and acquisition module, an alarm module, a sensor group, an aerosol fire extinguishing module, a communication module and a fire extinguishing plug body. The extinguishing plug body provided by the invention hasthe functions of rain prevention, dust prevention and lightning protection. The upper part of the fire extinguishing plug body are provided with display and alarm devices, and a side face of the fireextinguishing plug is provided with a maintenance door to facilitate the maintenance and repair of the fire extinguishing plug. The front side of the fire extinguishing plug is provided with a switchbutton for controlling the display parameters of the display device to be switched between gas concentration and temperature, a seam of the maintenance door is subjected to special processing so as to ensure the waterproof and dustproof performance of the seam. With the consideration of high temperature in summer and low temperature in winter, different alarm and fire extinguishing data combinations are set for the temperature and mixed gas concentration, and false alarm and missed alarm are effectively avoided. Through setting the system power supply, the high reliability and high stabilityof a power supply system of the fire extinguishing plug are ensured.