The project studied in this work is a part of the No.2 line of Beijing subway, which connects the Jishuitan station and the Gulou station. It is a straight tunnel with a double directions. The whole tunnel line is 1290 m long without considering the horn meatus. The fan which used for ejecting smoke is located at position 660-670 m away from the Jishuitan station. The fan is axial type. The operating parameters of fan are: mass flow quantity of 55m3/s; pressure of 50Pa; loose speed of 740rpm and power of 55KW.