In　this　paper,　according　to　analyzing　the　domestic　and　foreign　recent　research　status　and　future　developments　of　open　architecture　CNC　system,　an　open　soft　system　with　configurable　architecture　based　on　PC　+　programmable　I/O　interface　card　has　been　studied.　The　research　is　studied　for　the　drawbacks　of　existing　open　CNC　system　based　on　PC　and　the　unresolved　problems　of　preliminary　study　presented　by　the　research　group,　to　satisfy　the　development　requirements　of　low　cost,　high　performance　that　means　high　speed,　high　precision　and　the　large　amount　of　data　processing,　configurable　architecture　and　modularization.　Meanwhile,　this　dissertation　makes　systematic　and　deep　going　study　on　function　requirements,　structure　planning　based　on　programmable　I/O　interface　card,　hardware-configurable　modeling,　circuits　design　of　control　chip,　task　assigning　between　software　and　hardware　and　servo　control.