<p>The cutting environment for ball-end milling cutters in numerical control (NC) milling is notably challenging, particularly when utilized for machining complex surfaces. Controlling fluctuations in the main cutting force under such conditions poses significant difficulties. Additionally, the detrimental impact of an adverse cutting environment on the overall milling outcome cannot be overlooked. To ensure manufacturing quality, a study has been conducted on the algorithm of the main cutting force, aimed at minimizing the influence of force variations on processing quality during the milling of complex surfaces with a ball-end milling cutter. This approach also seeks to maintain the effectiveness of NC milling products. Initially, a geometric model is established using the micro-element method when an elliptical paraboloid is machined by a ball-end milling cutter. Based on this foundation, an algorithm model for the main cutting force is developed within this cutting environment, leveraging fundamental concepts of metal cutting and relevant mathematical principles. The validity and effectiveness of the main cutting force algorithm are subsequently confirmed through Matlab simulations, actual cutting experiments, and comparisons between simulation results and empirical data collected from cutting experiments. This algorithm accurately predicts the main cutting force exerted by the ball-end milling cutter during the milling of complex surfaces. Overall, the algorithm serves as a powerful guide for ensuring quality in actual NC milling processes.</p>