Color　measurement　and　control　system　can　improve　the　product　quality　and　efficiency　of　multi-color　offset　printing,　and　the　technology　of　color　to　ink　conversion　is　one　of　the　key　technologies　of　the　color　measurement　and　control　system.　First,　the　principle　of　the　automatic　color　measurement　and　control　system　is　given,　then,　the　relationship　between　the　quality　parameter,　such　as　the　density,　and　ink　amount　is　analyzed,　and　the　conversion　matrix　between　chroma　and　density　is　given.　On　the　basis,　color　to　ink　conversion　algorithm　based　on　density　and　color　to　ink　conversion　algorithm　based　on　chroma　are　designed,　and　the　relevant　algorithm　flow　diagrams　are　given.　The　algorithms　are　applied　to　the　color　measurement　and　control　system.　When　there　is　density　deviation　or　chroma　deviation,　the　algorithms　can　calculate　the　adjustment　of　the　ink　key　automatically　to　change　the　ink　amount,　then　improve　the　color　quality　of　the　print.