The inhibition effects of ultrafine mists of 5%, 8%, and 15% water/NaCl solutions on 6.5%, 8%, 9.5%, 11%, and 13.5% methane explosions were experimentally studied in a closed vessel which was equipped with two tempered glasses in the front and back sides respectively. Ultrafine water/NaCl solution mist was generated in the vessel directly by ultrasonic atomization method, and mist size was measured by a phase doppler particle analyzer. Explosion flame evolution processes under different spraying conditions were recorded by a high-speed camera. The relationship between pressure rising and flame propagation was analyzed. Results indicate that explosions could be suppressed by ultrafine water/NaCl solution mists. Moreover, the inhibition effects, which were characterized by reductions in the flame propagation speed, the maximum explosion overpressure (Delta P-max), and the maximum pressure rising rate ((dP/dt)(max)), could be improved by increasing the water/NaCl solution concentration and mist amount. The pressure underwent two accelerating rises and was influenced obviously by solution concentration. The absolute inhibition of methane explosion was influenced by the water/NaCl solution and methane concentrations. The mist amount required for absolute inhibition of the explosion decreased after addition of more NaCl to the spraying solution. The enhancement in inhibition of methane explosion was due to the combination of improved physical and chemical effects. (C) 2016 Elsevier Ltd. All rights reserved.