In　this　paper,　two　kinds　of　different　sliding　bearing　support　structure　including　a　traditional　cross-shaft　and　a　semi-shaft　are　designed　for　a　water　hydraulic　pump.　The　characteristics　of　the　two　sliding　bearings　in　each　structure　are　calculated.　By　comparison,　it　is　found　that　the　working　conditions　of　the　two　sliding　bearings,　especially　the　pv　value,　in　the　semi-shaft　support　structure　are　near　to　be　identical　in　the　cross-shaft　one,　which　will　be　helpful　to　prolong　their　service　life.　Based　on　the　Stress-strength　interference　theory,　a　reliability　calculation　model　of　the　friction　pair　between　the　shaft　and　sliding　bearings　is　proposed.　The　analysis　results　indicate　that　the　semi-shaft　sliding　bearing　support　is　beneficial　to　largely　raise　the　inherent　reliability　of　the　water　hydraulic　pump　as　well　as　the　service　life　of　the　pump.　©　2011　IEEE.