It　is　an　expectation　of　most　of　the　numerical　control　products　manufacturer　that　have　a　powerful　controller　with　whole　won　intellectual　property　and　without　restriction　from　other　companies.　The　paper　introduces　a　new　type　of　motion　controller　that　based　on　ARM　and　EtherCAT　field　bus.　It　concludes　the　analysis　and　porting　method　of　the　EtherCAT　soft　master　source　code,　and　how　to　modify　the　driver　of　dm9000　to　make　EtherCAT　master　works　correctly.　It　also　gives　an　example　to　confirm　the　reliability　of　the　controller.　Since　ARM　has　an　open　architecture,　EtherCAT　soft　master　does　not　depend　on　any　special　hardware　card,　and　Linux　OS　is　an　open　source　system,　this　controller　has　open　and　flexible　characteristic　both　on　hardware　and　software.