Abstract: In view of problems that dry powder fire extinguishing agent will cause pollution, difficult cleaning and equipment damage, a high-pressure water mist automatic fire extinguishing system for flammable dust environment was designed. High-pressure energy storage system generates high-pressure water immediately and rapidly forms high-pressure water mist after flame sensor detects flame signal of flammable dust combustion, and then water supply system is quickly pressurized to working pressure, replaces high-pressure energy storage system to provide high-pressure water and continue to generate high-pressure water mist. The test results show that the high-pressure water mist automatic fire extinguishing system for flammable dust environment has fast response speed, average response time of flame sensor and controller is 4 ms and 12 ms respectively; high-pressure water mist generation is fast and average generation time is 96 ms, the longest generation time is 100 ms; the fire extinguishing is effective and timely, after the high-pressure water mist acts on combustion flame for 1 s, the combustion flame is basically extinguished, and the propagation and diffusion of combustion flame stops when propagates to about 0.2 m from the center ignition position. It is verified that the system can effectively avoid spread of flammable dust combustion flame and prevent flammable dust fire accidents.