Abstract: The method for adjusting the equivalent length in the ventilation and smoke extraction model test for long traffic tunnels is still immature. Based on the running tunnel section between Wawuzhuang Station and Guizhou Road Station of Qingdao Metro Line 1, a tunnel model test platform was built. A throttle ring was installed to control the tunnel air outlet area and change the pressure drop, achieving active adjustment of the model’s equivalent length. Thirty-one sets of variable parameter tests were conducted using numerical simulation methods to reveal the impact of area ratio on the model's equivalent length. On this basis, the air outlet shapes were changed, and simulations for multiple sets of area ratio conditions were completed. The research results show that when the area ratio is between 0.133 and 0.735, the calculated equivalent length of the traffic tunnel ventilation model is between 21.86 m and 362.53 m. Inverse verification through numerical simulation shows that the tunnel model's equivalent length only depends on the area ratio and is independent of the air outlet shape and the model's original length. The air outlet area ratio is the core parameter for adjusting the equivalent length.