<p>Existing spline partitioning methods exhibit poor applicability to the free-bending process. Addressing this limitation, this paper innovatively proposes a spline partitioning and processing method that explicitly considers the transition section. Our approach accounts for the influence of the transition section length within a pipe fitting on the axis deviation of the formed part. The method uniformly partitions the spline portion of the pipe fitting, using the maximum transition section length as the partitioning unit. Furthermore, we analyze the causes of deviation between the spliced model and the theoretical model within the spline region after partitioning. To address this deviation, we employ a combination of planar arcs, positioning chords, and variable chord angles to reconstruct the spline portion. This ensures the reconstruction error between the spliced model and the theoretical model remains within acceptable limits. Additionally, the relationship between the variation in the tangent vector angle across the spline and the vertical displacement of the bending die is derived, thereby yielding the necessary processing parameters for forming this section. Validation through application to typical parts confirms the effectiveness of this partitioning and processing method in actual pipe fitting forming.</p>