Now,　the　registration　precision　usually　adjusted　by　handwork　that　is　an　undeveloped　method　for　multi-color　printing　machines　in　china.　To　solve　this　problem,　an　automatic　detection　method　of　color　registtration　is　proposed.　Registration　marker　image　is　photographed　on　the　basis　of　visual　imaging　principle,　and　the　calculation　method　of　registration　deviation　is　established　by　adopting　the　image　analysis　theory.　Marker　images　are　preprocessed　by　using　the　vector　signal　filtering　method　of　color　image,　and　image　objects　are　extracted,　so　a　color　recognition　model　for　cyan,　magenta,　yellow　and　black　primary　colors　and　their　complex　color　pixels　is　derived.　The　next　step　is　that　edge　pixels　of　color　marker　are　extracted,　and　their　structural　lines　are　approximated　by　least　square　fitting　and　Hough　transform　method.　At　last,　relative　distances　among　registration　markers　on　image　are　calculated　and　translated　into　relative　distances　in　object　space　via　vision　calibration　methods.　Experiments　indicate　that　precision　of　20　micron　is　obtained　when　this　automatic　detection　method　is　applied.　And　this　accords　with　general　printing　technology　standard　of　china.　This　method　can　be　applied　to　two　or　four　color　offset　printing　system　based　on　the　CMYK　synthesis　principle.　©　2009　Journal　of　Mechanical　Engineering.