A milling force prediction-based curved surface processing trajectory generation method relates to the metal milling processing field, and can limit the fluctuation of a milling force during a processing process, and improve the surface quality of a workpiece and the processing efficiency. The method comprises the steps of discretizing and dividing a workpiece curve; establishing a vector diagram of the forces of the discrete points, and calculating the milling force; selecting a discrete point at random as an initial point, calculating the positions of the nearest eight discrete points of the initial point; calculating the differences of the milling forces of the initial point and the nearest discrete points in the same direction, and comparing the differences to obtain an optimization connection direction of an initial cutting point; taking the nearest discrete point in the optimization connection direction as the next cutting point, and calculating the positions of the nearest eight discrete points of the next cutting point; obtaining an optimization connection direction of the cutting points by using the above method, repeating the last step until all discrete points are connected, thereby obtaining a tool path trajectory in the actual processing. The milling force prediction-based curved surface processing trajectory generation method of the present invention is used for the free curved surface cutting processing.