The invention relates to the field of pipeline tapping. In order to improve tapping efficiency and tapping precision, the invention provides a tapping method for a pipeline arc surface. The method comprises drawing an axial positioning line, a peripheral positioning line, a profile line of a pipe platform mounting hole and a cutting line; setting cutting-starting points A' and B' and pre-stopping points C and D; mounting a cutting torch support adjusting device comprising a rotary shaft, an adjusting vertical rod and an adjusting cross rod on a tapping pipeline, and sleeving a fixing sleeve on the lower end of the rotary shaft and vertically fixing on the tapping pipeline; adjusting the cutting torch support adjusting device and starting cutting torque for preheating till a preheated region is in a range of 150-250 DEG C, and closing the cutting torch; adjusting the cutting torch support adjusting device, cutting from the cutting-starting points A' and B' to the pre-stopping points C and D along the cutting line, and closing the cutting torch; detaching the cutting torch support adjusting device, and handholding the cutting torch to cut the rest part along the cutting line till cutting is finished. By adopting such tapping method for a pipeline arc surface to tap the pipeline arc surface, the tapping efficiency and tapping precision are high and operation is simple and convenient.