The　latest　development　trend　of　direct-drive　electro-hydraulic　servo　technology　is　discussed.　The　working　principle,　system　model　and　system　control　theory　of　an　electro-hydraulic　servo　system　are　studied.　The　dynamic　behavior　of　the　direct-drive　electro-hydraulic　servo　system　is　highly　nonlinear,　structure　uncertainty.　Considering　that　the　standard　PID　controller　cannot　fulfill　all　the　demands,　it　is　necessary　to　use　advanced　means　for　compensation.　A　PID　controller　optimized　by　genetic　algorithm　for　an　electro-hydraulic　servo　system　direct　driven　by　a　permanent　magnet　synchronous　motor　is　proposed.　The　genetic　algorithm　is　applied　to　optimize　the　parameters　of　the　PID　controller.　The　simulation　and　experiment　research　of　one　direct-drive　electro-hydraulic　servo　system　are　carried　out　to　verify　the　response　properties　of　the　proposed　controller.　The　step　signal　tracking　responses　of　the　servo　system　with　different　parameters　of　PID　controller　are,　respectively,　reported.　In　addition,　a　feedforward　PID　controller　using　genetic　algorithm　optimization　is　also　designed　for　the　direct-drive　servo　system.　The　simulation　and　experiment　results　show　that　the　feedforward　PID　controller　using　genetic　algorithm　optimization　has　good　dynamic　response　characteristics　in　the　electro-hydraulic　servo　system　based　on　a　direct-drive　permanent　magnet　synchronous　motor.　©　2018,　The　Natural　Computing　Applications　Forum.