Cloud　computing　has　emerged　as　a　new　paradigm　for　services　delivering　over　the　Internet.　In　this　growing　market,　PaaS　(Platform-as-a-Service)　cloud　has　been　an　important　model　allowing　a　simple　and　flexible　deployment　of　applications,　without　the　need　for　dedicated　networks,　servers,　storage　and　other　services.　Many　PaaS　services　have　been　provided　in　the　past　few　years　and　it　is　required　to　use　hybrid　PaaS　services　in　order　to　satisfy　management　requirements　such　as　legacy　system　integration　and　dynamic　resource　scaling.　However,　there　are　various　management　interfaces　and　different　management　mechanisms　among　PaaS　clouds,　which　cause　great　difficulty　and　high　complexity　to　application　deployment　in　a　hybrid　cloud.　In　this　paper,　we　present　a　runtime　model　based　approach　to　using　hybrid　PaaS　services.　First,　the　manageability　of　PaaS　services　is　abstracted　as　runtime　models　that　are　automatically　connected　with　the　corresponding　systems.　Second,　we　provide　a　unified　model　of　PaaS　services,　according　to　the　domain　knowledge　of　current　PaaS　clouds.　Third,　the　synchronization　between　the　unified　model　and　runtime　models　is　ensured　through　model　transformation.　Thus,　administrators　are　able　to　use　hybrid　PaaS　services　in　a　unified　manner　and　management　logic　can　be　also　carried　out　by　executing　programs　on　the　unified　model,　which　decreases　the　difficulty　and　complexity　of　hybrid　cloud　management.