Abstract:To evaluation the effects of rock phosphate(enriched with sulphur,organic matter and thiobacillus bacteria) and Triple Super-Phosphate(TSP) on orange trees(citrus sinensis) fruit yield and quality, an experiment with 8 treatments and three replications, was conducted in a randomized complete block design, in Dezful agricultural research center (southwestern Iran). Treatments included: 1-control, 2-200 g P2O5 from TSP, 3-400 g P2O5 from TSP, 4-600 g P2O5 from TSP, 5-400 g P2O5 from rock phosphate, 6-5+compost of sugar-can bagasse,7-5+600 g thiobacillus inoculate, 8-800 g P2O5 from rock phosphate.Yield and number of fruit, significantly increased(p<0.05) by rock phosphate(79 vs. 111 kg tr-1) and TSP(79 vs. 108 kg tr-1) application. The treatments significantly increased the size, ascorbic acid and juice content of fruit. It was concluded that the rock phosphate plus amendments can use, instead of triple super-phosphate as a source of P for orange tree nutrition. Keywords: citrus, rock phosphate, triple super-phosphate, yield, quality.