Electro-hydraulic　servo　steering　system　(EHSSS)　has　been　widely　used　in　multi-axle　heavy　vehicles.　Noteworthy,　the　traditional　EHSSS　controlled　only　by　servo　solenoid　valve　has　amounts　of　energy　loss　in　throttling　orifice.　Although　the　steering　control　accuracy　is　ensured,　it　leads　to　low　energy　efficiency.　In　this　paper,　a　novel　pump/　valve　combined　control　(PVCC)　EHSSS　is　proposed　to　increase　the　energy　efficiency,　which　only　uses　one　servo　motor　pump　and　one　servo　solenoid　valve　to　drive　the　steering　trapezoid　mechanism.　Based　on　the　control　objectives　of　low　pressure　difference　in　valve　orifice　and　high　steering　tracking　performance,　a　dual-input-dual　output　control　strategy　is　proposed.　To　guarantee　the　high　steering　tracking　performance　of　PVCC　steering　system,　a　high-gain　observer　based　sliding　mode　controller　(HGO-SMC)　is　designed　for　controlling　the　spool　displacement　of　servo　solenoid　valve.　During　the　steering　process,　the　servo　motor　pump　is　controlled　by　a　simple　speed　feedforward　and　PID　controller,　so　that　the　pressure　difference　in　throttling　orifice　is　kept　at　a　low　value　to　reduce　the　energy　wasted.　The　experimental　comparison　results　show　that　the　proposed　method　can　achieve　the　same　tracking　performance　as　valve　control　EHSSS　with　less　energy　consumption.