The full scale simulation cabin and pumping pressure water mist system were employed to study the validity of the obstacle fires extinguishment by water mist on the conditions of different obstacles baffles. The validity of water mist system and main influencing factors on the extinguishment of the obstacle heptanes fires were analyzed. FDS (4.0.5) was employed to study the interaction of the water mist and obstacle oil fires and the extinguishing rules and factors were determined primarily. The experimental and simulation results show that the structure and style of the obstacle fires are important to influence the validity of the obstacle fires extinguishment by water mist. The more the water mist is entrained by the airflow, the more effective of the extinguishment by water mist.