The disclosure discloses a method for constructing actual processing curve of part with small curvature based on a point cloud boundary. The method includes: (a) encrypting a three-dimensional ordered boundary curve of a part to be processed; (b) fitting encrypted boundary points into a plane, and projecting each boundary point into the plane to obtain a projection point; (c) performing Euclidean cluster within the plane to obtain point sets, and fitting the obtained point sets into a straight line; (d) performing the Euclidean cluster on projection points that are not fitted into the straight line to obtain corner point sets, and fitting a sharp corner or a rounded corner of the corner point sets to obtain a fitted boundary curve within the plane; (e) mapping the fitted boundary curve to a curved surface of the three-dimensional ordered boundary curve to obtain an actual processing curve of the part to be processed.