One of difficulties in super long tunnels’ construction is the construction ventilation to meet the requirement of normal construction environment and assure the workers’ health. Using traditional tunnelling ventilation is very difficult to meet the need of super long tunnel construction. As the energy assumption is high and it is very expensive. This paper investigated the simulation of tunnel construction ventilation with large power jet fans during the construction of Jinping Auxiliary Tunnels by using the computational fluid code FLUENT, the layout of jet fans in the tunnels is optimized. It is found that the best layout of the jet fan is aroud the transverse channel under the direction of airflow and jet fan should not be too far away from the transverse channel. The CO mainly distributes in the upper part of the tunnel when the jet fan is installed at a higher position, this layout of the jet fan is beneficial to construction of tunnels.