In　this　paper,　a　novel　method　of　measuring　the　interface　of　muitiplayer　material　(for　example,　between　the　two　kinds　of　liquid)　based　on　machine　vision　is　proposed.　The　interface　information　is　firstly　transformed　into　two-dimension　image　by　imaging　device.　Then　boundary　between　materials　is　detected　by　edge　detection　method.　Because　there　is　very　low　gray　difference　between　different　materials　in　the　acquired　image,　the　borderline　is　very　blurry　and　difficult　to　be　detected.　In　this　paper,　a　novel　algorithm　of　edge　detection　is　proposed　for　the　boundary　detection　on　the　above　special　instances.　For　above　obtained　discontinuous　interface　outline,　a　new　method　for　the　curve　smoothness　is　suggested.　The　experimental　results　show　the　validity　of　proposed　method,.