The invention discloses a bending following method and a sheet metal bending process based on a robot additional shaft. The bending following method comprises the following steps: S1, establishing a user coordinate system; S2, adopting a robot to grab a sheet metal to put the sheet metal on the upper surface of a die flatwise, and coinciding a tool coordinate system with the user coordinate system; S3, establishing the geometrical relationship between the distance from the bending part of the lower surface of the sheet metal to the upper surface of the die and the single-side bending angle ofthe sheet metal, and calculating bending following dynamic points to generate the bending following action program of the robot; S4, carrying out inverse solution on the point location position of themoving process of the robot, judging whether the robot meets the accessibility requirement, if yes, finishing the bending action, otherwise, carrying out step 5; and S5, according to the robot angleconfiguration, calculating the following drawing pace of the additional shaft, and if the additional shaft moves to a new position with the drawing pace multiplying the adjusting times of the drawingpace, returning to S3. With adoption of the bending following method, efficient and reliable automatic bending of the sheet metal is realized.