The invention relates to a method for controlling the welding path of a welding robot. A control system detects and adjusts the position and posture of a welding gun in real time, so that the welding gun is always positioned right above a welding seam. Moreover, the control system judges an energy difference value detected by an energy detector according to received information; if the absolute value of the difference value is less than a preset threshold valve, the control system does not adjust the posture of a mechanical arm; if the difference value is greater than or equal to the threshold value, the control system issues a movement command to the mechanical arm and controls the mechanical arm to adjust the posture, until the difference value is less than the threshold value and the welding gun moves to right above the welding seam and is vertical to be plane of a plate.