This paper described full-scale tests of water mist fire suppression system under forced desmoking conditions. Pool fire was effectively suppressed in 25.0 and 37.0 s for 1,500.0 (test 1) and 3,000.0 (test 2) mL of oil with no ventilation, respectively. Moreover, under ventilation rates of 50.0 and 75.0 m3/min, the suppression time were lengthened to 54.0 s (test 1) and 202.0 s (test 2), and 102.0 s (test 1) and 222.0 s (test 2), correspondingly. However, the smoke exhaust had a strong effect on the water mist to result in fire could not extinguish, when the ventilation rate increased to 120.0 m3/min. The temperature distribution during the early period in the scenario of no ventilation has a higher magnitude than those scenarios of 50.0, 75.0, and 120.0 m3/min, because combustion proceeds smoothly to result in temperature increased rapidly at no ventilation. Furthermore, similar results presented in smoke concentration distribution at four scenarios (0, 50.0, 75.0, and 120.0 m3/min), and combustion occurred steadily at no ventilation to result in more smoke during the early period. This study employed a computer modeling to verify water mist system in a compartment space and determine how the water mist system could be optimized.