This paper presents an improved trimming algorithm. When cutting each pattern on the mesh surface, the algorithm first checks if a patch has been modified by other patterns, and then cuts the patch set with the new topology caused by the current pattern and updates the resultant patch set. Finally the algorithm removes the vertices and faces from the mesh surface inside the closed paper-cutting pattern to achieve cut-out effects observed from hand made paper cutting works. 3D Paper-cutting has wide applications ranging from animation, education to entertainments.