In　the　design　of　stand-alone　hybrid　wind/photovoltaic　(PV)　power　system,　the　optimal　sizing　is　an　important　and　challenging　task.　The　coordination　among　renewable　energy　resources,　generators,　energy　storages　and　loads　is　very　complicated.　The　sizing　of　stand-alone　hybrid　wind/PV　power　system　can　be　considered　as　a　multi-objective　optimization　problem　involving　two　conflicting　objectives:　maximization　of　power　reliability　and　minimization　of　cost.　The　loss　of　power　supply　probability　(LPSP),　which　is　the　index　of　power　reliability,　is　obtained　by　simulation.　The　Pareto　optimal　solutions　were　found　using　the　elitist　non-dominated　sorting　genetic　algorithm　(NSGA-II),　and　was　validated　by　solving　the　multi-objective　problem　with　a　traditional　method,　which　also　belongs　to　the　e-constraint　method.　The　decision　variables　are　not　only　the　size　of　solar　PV　panels　and　the　capacity　of　batteries　in　traditional　methods,　but　also　the　type　and　size　of　wind　turbine　generators　and　the　tilt　angle　of　PV　panels.