Abstract: The pool fire tests were conducted to evaluate the water mist system’s ability to extinguish relatively liquid fire. In order to investigate the heptane pool fire suppression with a water mist fire suppression system, a series of experiments were performed in an enclosed compartment of 4.6m×3.3m×4m(L W H)with variable distance of heptance-to-brim. Thermocouples and gas analyzer were used to measure the temperature and gas concentration in the flame. The effection of heptance-to-brim to the effectivity of water mist suppressing pan fire was gained, which provides corresponding experimental foundation for designing water mist system, establishing test standard and developing new product of water mist.