The blast fence can generally be divided into integral fence and louver fence. Based on the purpose of analyzing blast fence's effect., the paper builts jet flow field model , simulated effect on jet flow field of different installation forms. Equation is scattered by standard format, and coupling of pressure and velocity use simple algorithm. The model applied Cartesian co-ordinates, and used structural grid. Simulation results indicate that blast fence's effect is obvious. And if the integral fence is too high or too steep, it can produce abundant airflow. The louver fence make airflow spread towards the back and above along the blade, and its air resistance is lower than the other one's.