Traditional　optimization　methods　of　installed　wind　power　capacity　do　not　take　the　impact　of　wind　power　fluctuation　on　the　total　operating　cost　of　system　into　account,　thus　leading　to　blind　expansion　of　wind　farms　and　deterioration　of　wind　power　curtailment.　In　this　paper,　wind　power　fluctuation　cost　is　introduced　to　optimize　the　installed　capacity　of　a　wind　farm.　Firstly,　taking　the　net　present　value　of　the　social　benefit　of　a　planned　wind　farm　as　optimization　objective,　a　chance　constraint　programming　model　is　established　considering　the　constraints　such　as　system　power　balance,　conventional　generator　operation,　grid　transmission　capacity　limit,　system　reserve　requirement　and　so　on,　where　the　optimal　and　sub-optimal　solutions　of　installed　capacity　of　the　wind　farm　are　obtained.　Secondly,　the　installed　capacity　intervals　to　be　assessed　are　set　up　based　on　above　solutions.　Then,　a　hybrid　multi-attribute　evaluation　based　on　determination-uncertain　(D-U)　space　of　set　pair　analysis　(SPA)　is　adopted　to　investigate　the　comprehensive　performance　of　the　both　intervals　with　the　evaluation　indicators　involving　the　net　present　value　of　the　social　benefit　of　the　wind　farm,　wind　curtailment　rate,　transmission　safety　margin　and　power　shortage　risk.　Effectiveness　of　the　proposed　method　is　verified　with　case　analysis　contrastive　with　existing　methods.　©　2019,　Power　System　Technology　Press.　All　right　reserved.