Abstract: FDM (fused deposition modeling)is an additive manufacturing technology that uses thermoplastic bonded materials to manufacture products by printing layer by layer.In this paper, an automatic generation algorithm of octa-prism support structure based on STL format is designed by Matlab.The algorithm can identify and extract the area to be supported.The identified area to be supported is projected onto a two-dimensional plane, and isometric sampling is executed in the projected area.The height of the model above the sampling point is calculated, and the supporting structure is automatically generated to achieve structural optimization.The algorithm can effectively save printing time and materials on the premise of ensuring printability.The results show that the algorithm saves 27.23% of materials and 14.85% of printing time compared with Cura software.