In　this　paper,　a　risk　explicit　interval　two-stage　programming　(REITSP)　model　was　proposed　for　supporting　the　regional　electricity　generation　expansion　with　renewable　portfolio　standard　(RPS)　constraint.　It　could　effectively　tackle　multiple　uncertainties　expressed　as　interval　numbers.　But　unlike　the　traditional　interval　two-stage　programming　model,　the　proposed　REITSP　model　could　provide　an　explicit　trade-off　information　between　system　cost　and　risk　for　decision　makers　with　different　risk　preferences.　It　could　minimize　the　total　system　cost,　as　well　as　the　decision　risk　according　to　the　aspiration　risk　level　of　decision　maker.　The　developed　REITSP　model　was　applied　to　the　case　study　in　Guangdong　Province,　China　for　its　long-term　electricity　system　planning.　Crisp　solutions　under　different　aspiration　risk　levels　for　varying　RPS　targets　were　obtained　and　analyzed.　The　results　showed　that　according　to　the　current　available　renewable　energy　and　affordable　construction　speed,　the　maximum　RPS　target　for　Guangzhou　Province　during　2016-2025　should　be　17%.　Higher　RPS　level　would　promote　the　renewable　energy　generation,　especially　solar　power;　meanwhile,　it　would　reduce　the　CO2　emission　and　the　imported　electricity,　but　with　greater　investment　cost.　The　obtained　results　and　trade-off　information　would　be　valuable　for　the　optimal　long-term　electricity　system　expansion　planning　when　facing　future　uncertain　situation.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.