Offshore　wind　power　resource,　which　is　relatively　stable,　abundant,　and　with　modest　impact　on　the　environment,　is　a　kind　of　clean　and　renewable　energy　suitable　for　large-scale　development.　Offshore　wind　farms　have　different　topological　structures　of　the　collection　system,　such　as　AC　parallel　type,　DC　parallel　type,　DC　series　type,　single-ring　type,　and　double-ring　type.　The　purpose　of　this　paper　is　to　analyse　reliability　and　economy　for　various　topologies　and　provide　an　insight　into　wind　farm　construction.　In　this　study,　the　topology　structure　of　various　offshore　wind　farms　is　introduced　firstly.　Then,　the　reliability　assessment　methods　are　proposed.　The　reliability　of　the　chain　wind　farm　is　analysed　with　the　reliability　block　diagrams,　while　the　reliability　of　the　ring　wind　farm　is　analysed　by　using　the　classification　method.　In　addition,　the　economy　is　evaluated　considering　investment　costs.　The　investment　cost　for　each　type　of　component　is　calculated　separately,　which　contributes　to　assessing　the　investment　cost　of　the　whole　offshore　wind　farm.　Detailed　results　from　a　case　study,　which　includes　96　wind　turbines,　demonstrate　that　the　DC　series-parallel　wind　farm　has　superiority　in　reliability　and　economy,　as　well　as　in　terms　of　its　potential　applications.　©　2019　Institution　of　Engineering　and　Technology.All　right　reserved.