Coil system is the core component of a tubular heating furnace, and bends are critical connecting elements within it. This paper uses Fluent to study the flow resistance characteristics of sharp bends and reducing bends in vacuum furnaces to obtain the velocity distribution, pressure distribution and streamline pattern along the flow path and at each cross-section inside the bends, and summarizes the influence laws of vaporization rate, inlet flow velocity, diameter ratio and bend diameter ratio on pressure drop. Results show that sharp bends outperform reducing bends in terms of pressure drop. The flow inside the bends presents characteristics of helical flow, double-vortex secondary flow, and even four-vortex secondary flow. The flow inside the bends has a significant influence on the downstream affected area, and the pressure drop of the bends shows a parabolic variation trend with the increase of vaporization rate and flow velocity.