The invention belongs to the multi-axis numerical control machining technical field, and relates to a multi-axis numerical control machining spiral path forming method based on radial curve interpolation; the method comprises the following steps: discretizing a machining curved surface into a triangle network model; building mapping relations between a grid curved surface and a planar circular domain one by one according to deformation mapping; evenly sampling the circumference of the circular domain, and forming a radius line; inversely mapping the radius line of the circular domain onto themachining curved surface according to the linear interpolation on the grid edge, thus forming a radial curve on the curved surface; carrying out spiral linear interpolation for the radial curve on said basis, and forming a segmented linear spiral locus; finally using a B-splint curve smooth the spiral locus, thus forming a smooth and continuous spiral numerical control machining path. The spiral numerical control machining path formed by the method can realize continuous machining of a part curved surface, can prevent cutter lifting and retracting in machining, and can ensure the smoothness ofthe cutter motions, thus improving kinetics and dynamics performances of the numerical control machine tool processing complex curved surface parts.