Abstract: This paper points out the shortcomings of traditional vehicle-mounted fire extinguishing system in underground coal mines. The advantages and disadvantages of water spray fire extinguishing system are analyzed, and the feasibility of vehicle-mounted water spray fire extinguishing system is discussed. In addition, a vehicle-mounted water spray fire extinguishing system is designed combined with the characteristics of trackless tyred vehicle with the explosion-proof diesel engine. The system is based on the normal pressure dry pipe network, and has the vehicle-mounted water source and air source, as well as the integrated fire source detector and water spray nozzle, thus the fire detection and automatic response is realized. The action mechanism, component configuration and arrangement mode of the control system are discussed. Furthermore, the main parameters of the fire extinguishing system are calculated.