Abstract: Aiming at the problem of the ventilation flow field in multi-working face construction of the super long gas tunnel, taking Yangzong tunnel as the supporting project, the numerical simulation software FLUENT is used to analyze the ventilation flow field and gas migration law at the left and right tunnels, cross passages and parallel adit and verify it with the field measured data. The research results show that the ventilation flow field is in a stable state after 10 minutes of ventilation. The ventilation flow field of the right tunnel under the stable flow field is divided into the impingement jet zone, the vortex zone and the reflux zone. Since the air duct of the left tunnel is relatively far from the tunnel wall, the vortex zone will also be formed on the side near the wall of the air duct. During the construction, the air duct should be close to the tunnel wall; After stabilization, the wind speed of the left and right tunnels, cross passages and parallel adit is greater than 0.5 m/s, which meets the requirements of the tunnel site con? struction; At the initial stage of ventilation, the gas is mainly concentrated in the face area, and the gas concentration in the vault on the opposite side of the air duct at the face is significantly higher than that in other areas; The changing trend of gas concentration at the left and right tunnel face is first slowly rising and then suddenly falling. The change of gas concentration in the face area mainly depends on the gas concentration and emission intensity of the face.