A　handwriting　detecting　system　based　on　Micro-gyros　and　Micro-accelerometer　is　proposed.　And　the　algorithm　of　the　detecting　system　is　also　described　in　detail.　And　the　error　analysis　of　the　detecting　system　is　also　described　in　detail　.The　motion　contrail　of　the　handwriting　detecting　in　the　3-D　space　can　be　recognized　through　compute　the　matrix　of　attitude　angles　and　the　dynamic　information　of　the　handwriting　detecting　which　is　mapped　on　the　2-D　plane.　Then　the　information　of　contrail　can　be　recurred　on　the　writing　plane　by　integral.　There　were　good　results　in　the　actual　experiment.　©2009　IEEE.