The utility model provides a flange docking auxiliary device which comprises a hydraulic station and at least two C-shaped hydraulic clamping calipers. Fixing cushion pads are arranged at one ends of the hydraulic clamping calipers, the other ends of the hydraulic clamping calipers are provided with clamping oil cylinders, and the clamping oil cylinders are connected with the hydraulic station. Each hydraulic clamping caliper is installed on the upper end of a supporting rod, the lower end of the supporting rod is connected on a lifting platform through a universal mechanism, and the lifting platform is used for adjusting installing height of the hydraulic clamping calipers. The hydraulic station, the hydraulic clamping calipers and the lifting platform are all arranged on a movable trolley. The flange docking auxiliary device is simple to use, convenient to transport, capable of solving the problem that the phenomenon of mouth-turning when the flange is docked during the installing and repairing of the pipeline is time-wasting and effort-wasting to process, and in no need of high workload of workers, and improves safety factors of working staff.