Background:　Hydraulic　excavator　as　important　engineering　machinery　plays　an　extremely　significant　role　in　engineering　construction.　Multi-way　valve　is　the　core　element　of　hydraulic　system　of　excavator,　which　is　used　for　controlling　the　flow　of　oil　and　the　flow　distribution　of　actuators,　its　performance　has　important　implications　for　the　whole　machine.　Objective:　In　order　to　guide　the　design　and　optimization　of　spools　of　main　valve　of　a　medium　hydraulic　excavator　quickly,　a　numerical　simulation　model　of　hydraulic　system　of　working　device　was　built　based　on　AMESim.　But　it　is　impossible　to　simulate　the　ever-changing　load　accurately　just　with　numerical　simulation　method.　Methods:　To　make　up　the　shortage,　a　real-time　testing　system　for　excavator　based　on　CompactRIO　was　built.　Then　the　simulation　model　was　embedded　into　the　testing　system　through　interface　modules　to　establish　a　semi-physical　simulation　platform　for　hydraulic　system.　The　platform　was　used　to　test　and　simulate　the　hydraulic　system　of　the　excavator’s　working　device.　Results:　It　shows　that　the　simulation　results　are　in　good　agreement　with　the　measured　data,　which　means　the　platform　performs　well.　Conclusion:　The　platform　has　great　significance　to　accelerate　the　design　and　development　of　main　valves,　and　it　also　can　provide　strong　support　for　analysis　and　research　of　hydraulic　system　of　excavator.　It　could　be　of　great　significance　both　in　designing　multi-way　valve　and　reducing　the　debugging　cost.　©　2017　Bentham　Science　Publishers.