External　fixators　are　extensively　applied　in　the　treatment　of　lower　limb　deformities.　To　detect　the　positional　relationship　of　the　limb　and　external　fixator　during　the　distraction　osteogenesis,　an　interference　detection　algorithm　is　proposed.　The　algorithm　is　established　on　a　minimum　distance　model　of　cone-frustums　busbar　and　cylindrical　axis　using　vector　analysis.　The　models　of　3D　printed　cone-frustum　(CF)　are　used　to　perform　the　interference　experiment,　which　validate　the　feasibility　of　the　proposed　algorithm.　The　algorithm　can　assess　the　implementability　of　the　correction　path　to　ensure　the　safety　of　the　correction　strategy.