The　two-speed　electric　drive　automatic　transmission　(2EDAT)　is　an　effective　scheme　to　improve　the　economy　and　power　performance　of　electric　vehicles.　It　is　significant　to　carry　out　forward　design,　valve　body　improvement,　and　oil　circuit　optimization　of　the　hydraulic　system　for　2EDAT.　In　the　study,　the　functional　requirement　of　2EDAT　hydraulic　system　was　firstly　analyzed　and　key　parameters　were　calculated　to　determine　the　principle　design　of　the　hydraulic　system.　Then,　the　simulation　model　of　the　hydraulic　system　was　established　in　the　multidisciplinary　dynamic　simulation　platform　ITI-SimulationX　and　the　changes　in　the　pressure　of　the　main　oil　circuit,　the　clutch　oil　pressure,　and　the　cooling　and　lubrication　flow　in　the　shift　process　of　the　hydraulic　system　were　simulated　and　analyzed.　Furthermore,　according　to　the　principle　scheme　and　constraint　conditions　of　the　whole　machine,　the　overall　layout　and　the　hydraulic　valve　plate　of　the　hydraulic　system　were　designed　and　the　valve　plate　and　hydraulic　system　were　tested　on　the　bench.　The　test　results　of　clutch　pressure　were　5.73%–13.12%　lower　than　the　designed　value　and　did　not　meet　the　design　requirements.　Finally,　according　to　test　results,　the　processing　defects　of　the　pressure　reducing　valve　were　mitigated　and　the　main　oil　circuit　was　optimized　for　another　test　of　the　valve　plate　and　the　hydraulic　system.　The　test　results　of　clutch　pressure　were　0.35%–8.60%　higher　than　the　designed　value　and　met　the　design　requirements.　The　results　showed　that　the　optimized　hydraulic　system　realized　the　better　control　effects　on　the　main　oil　pressure　and　clutch　oil　pressure　in　the　shift　process,　including　the　fast　and　accurate　clutch　shift　response,　the　sufficient　cooling　and　lubrication　flow,　and　smooth　working　conditions.　©　IMechE　2023.