The　upgraded　metallurgical　silicon　(UMG-Si)　purified　by　a　metallurgical　process　route　directly　is　more　energy　efficient　than　the　conventional　Siemens　process,　but　high　metallic　impurities　are　the　cause　of　a　large　fraction　of　the　total　recombination　events　in　solar　cells　made　from　UMG-Si.　The　efficiency　of　crystalline　silicon　solar　cells　made　by　such　materials　is　lower　than　that　from　a　chemical　route,　and　UMG　solar　cells　have　big　light-induced　degradation.　So,　there　always　exist　debates　about　using　the　upgraded　metallurgical　silicon　for　photovoltaic.　In　this　paper,　the　impurity　contents　of　silicon　samples　obtained　in　different　stages　were　investigated,　and　a　four-year　verification　of　the　largest　UMG　photovoltaic　power　plant　in　the　world　was　conducted　for　the　first　time.　The　reliability,　operating　performance,　and　defects　of　UMG　photovoltaic　power　plant　were　analyzed.