There is no suitable condition to build any shaft(vertical or oblique shafts) due to the complex geological environment of Lianghekou. Furthermore, the tunnel has to be constructed blind heading. So the problem of ventilation is serious. Based on the theory of CFD，the wind current produced in forced ventilation is simulated by 3D RNG k-ε Turbulent Model，and then the Time-dependent Variation Rules of the flow field and the concentration field during the construction period are shown by numerical simulation of 3D. Results show that the backflow area which is located near the working face has the complex situation of wind current, and the air current distribution becomes stable gradually when it is far away from the backflow area. Meanwhile, the movement of the harmful air produced after blasting can be described as “moving” and “diffusing”. The result of moving makes the harmful air run out of the tunnel from working face. The result of diffusing makes the harmful air deliquated along with the process of moving. In addition, the time that the workers spend on getting into the tunnel has been studied according to the concentrations of CO (in and allowance concentrations respectively).