We　introduce　a　real-time　motion　control　system　that　uses　the　EtherCAT　protocol　and　apply　it　to　a　manipulator　with　six　degrees　of　freedom.　The　complexity　of　a　multi-joint　manipulator　leads　to　higher　requirements　for　synchronous　and　real-time　performance.　EtherCAT　technology　can　greatly　improve　the　performance　in　terms　of　accuracy,　speed,　capability,　and　band　width　in　industrial　control,　which　is　crucial　in　our　robot　projects.　In　this　paper,　we　discuss　a　servo　motion　control　system　based　on　EtherCAT　using　IgH　as　the　open-source　master　station.　A　Linux　operating　system　is　adopted　because　of　the　advantages　of　open-source,　high-efficiency,　and　high-stability　operation　as　well　as　multi-platform　support,　which　provide　more　flexibility,　freedom,　and　extendability　to　developers.　Considerable　research　has　been　conducted　to　explore　EtherCAT　technologies,　completely　implementing　home-made　codes　with　the　aid　of　open-source　libraries,　debugging　the　master-slave　communication　process,　and　testing　the　resulting　motion　controller　running　on　Linux　or　POSIX-compatible　operating　systems.　To　improve　the　real-time　response　of　servo　control,　a　real-time　Xenomai　kernel　has　been　compiled,　adopted,　and　tested,　and　it　showed　significant　enhancement　of　the　real　time　of　a　servo　motion　control　system.　Furthermore,　we　explore　trajectory　planning　and　inverse　kinematic　solutions.　A　trajectory　planning　method　based　on　B-spline　interpolation　of　three　degrees,　which　makes　each　part　of　the　trajectory　planning　curve　have　relative　independence　and　continuity,　is　proposed　for　the　kinematic　trajectory　planning　problem　in　Cartesian　space.　A　coordinate　system　is　established　using　the　modified　D-H　parameters　method　to　obtain　the　inverse　kinematics　of　the　manipulator.　The　simulation　and　experimental　results　show　that　the　calculation　speed　of　inverse　solutions　is　excellent　and　the　motion　of　the　manipulator　is　continuous　and　smooth.　©　2018　Fuji　Technology　Press.　All　Rights　Reserved.