<p>Aiming at the issues of support and step effect affecting model manufacturing accuracy and manufacturing time in the traditional 3D printing process, this paper proposes a 5-axis non-supporting adaptive slicing method based on the skeleton curve. For the model skeleton extraction problem, this paper determines the rotation axis through the start and end planes of the model, and each time the start plane is rotated to get multiple intersections with the model, and the intersection centroid is fitted using a smooth spline to get the model skeleton curve. For the 5-axis non-supporting adaptive slicing problem, the slice plane normal vector is determined from the tangent vectors of the model skeleton curves, the average cross-sectional area difference (ACAD) is proposed to measure the model manufacturing accuracy, the influence of the model geometric features on the model forming accuracy is analysed, and the adaptive slicing thickness formulae are established with the skeleton curvature and the model contour curvature as variables. Matlab simulation results show that for the free-form surface model, the adaptive slicing method in this paper reduces the number of slices by 26.5% compared to the 0.3&#xa0;mm 5-axis isothick slice algorithm. Compared with the 0.5-mm 5-axis isothickness slicing algorithm, the number of slices increases by 33.3%, and the ACAD decreases by 42.6%. Compared with the 5-axis isothickness slice algorithm, the 5-axis non-supporting adaptive slicing algorithm has obvious advantages when dealing with models with complex surface structures.</p>