The invention relates to a rotary water mist sprayer which is usually installed outside protected facilities, at safety evacuation exits, air wells and the like. The rotary water mist sprayer adopts a structure of dual-way rolling balls and dual-way O-shaped rings and is shaped as a mushroom. When the rotary water mist sprayer works, a high-pressure water source enters a mandrel through a filter screen and arrives at each spray core and spray nozzle of the sprayer body, the water flow is atomized into fine water drops less than 120 mu m to be sprayed, and the eccentric reacting force generated by each spray nozzle enables the sprayer body to rotate around the mandrel, and the water mist is sprayed in complete 360 DEG C. The invention belongs to the fields of fire control isolation, protection cooling and elimination of infrared radiation and radar signature of protected facilities. The rotary water mist sprayer is provided with a lock plunger, a filter screen, the mandrel, the rolling balls, screws, the spray cores, the spray nozzles, the spray body and the O-shaped rings and is widely applied to military industry, electric power, chemical industry, aerospace, ships, metallurgy, undergrounds and tunnels.