This　paper　forwards　a　low　power　design　of　a　grating　detection　system　chip　(GDC)　on　length　and　angle　precision　measurement.　Traditional　grating　detection　methods　are　complex,　costly,　and　suffer　big　power　consumption　for　the　complex　divide　circuit　scheme　and　CPU　software　compensation.　GDC　achieves　the　whole　grating　detection　system　function,　high　speed　orthogonal　signal　handling　in　a　single　chip　with　very　low　power　consumption.　It　is　an　application-specific　integrated　circuit　(ASIC),　integrated　micro　controller　unit　(MCU),　power　management　unit　(PMU),　two　LCD　controller,　keyboard　interface,　grating　detection　unit　and　other　peripherals.　Working　at　10MHz,　GDC　can　afford　5MHz　internal　sampling　rate　and　1.25MHz　orthogonal　signal　from　grating　sensor.　By　implementing　low　power　system　design,　orthogonal　signal　dividing　and　Low　power　divider　design,　GDC　consumes　0.9mw　in　test　mode　and　0.2mw　in　real　mode.　GDC　is　tape　out　in　HJTC　180nm　process　with　evaluation　kit　and　demo　system　developed.　©　2008　IEEE.