Abstract: The influence of the angle of cooling triangle on the inlet and outlet resistance is studied by numerical simulation. By placing cooling triangles with different top angles in the simulated wind tunnel, the pressure/velocity field distributions in front of and behind of the triangles under different wind speed conditions were simulated. The relatively uniform flow field sections of the inlet and outlet were intercepted, and the pressure drop and resistance coefficient of the inlet and outlet of the cooling triangle were obtained by subtracting the resistance of the radiator after the pressure difference was counted. The numerical simulation results were compared and analyzed with the commonly used inlet and outlet resistance coefficient calculation formulas. The results show that the two commonly used formulas can better estimate the inlet and outlet drag of cooling triangle in their applicable ranges. The calculation formula of the resistance coefficient for the inlet and outlet of the cooling triangle in the design manual of power engineering water supply is half theoretical and half empirical. Its assumptions about the fluid separation at the inlet of the finned tube and the reconstruction of the flow field after passing the radiator have been well verified by numerical simulation. The size of the angle of the cooling triangle has a great influence on the inlet and outlet resistance of the cooling triangle.A larger Angle can usually obtain a smaller inlet and outlet resistance.