In order to accurately estimate the influence of the interaction between pipeline laying and indoor air flow of the fan on the pressure drop loss, typical numerical analysis models and analysis workflow are established based on the underground utility tunnel project of Tanxinpei Road in Jiangxia District of Wuhan City. The inlet section and the stable section are analyzed respectively by establishing the 3D computational fluid dynamics(CFD) models of GIL cabin, highvoltage cabin and integrated cabin with typical pipeline layout, and the cyclic boundary conditions are used to consider the full development of the fluid in the stable section. The variation law of the resistance coefficient with different flow rates is obtained. The 3D model of typical exhaust vent of the GIL cabin is established, and the pressure drop losses of different fans in the fan chamber are analyzed and compared with the main normative estimates. The results show that: (1) The influence of pipeline layout on the pressure drop loss cannot be ignored. (2) The interaction of fans in the chamber is significant, and based on which the standards cannot accurately estimate the pressure drop loss.