This study is to evaluate the changes in the proximate composition of Sanh orange (Citrus nobilis L. Osbeck) cultivated in Vinh Long province, Vietnam. Commercial Sanh orange is graded into four following groups: first-grade orange, second-grade orange, ruffled orange, and tiny orange. In this study, physio-chemical properties of Sanh orange are examined on the flesh of orange while the bioactive compounds are examined on the peel of orange. General results showed that the ruffled and second-grade Sanh orange have the highest contents of vitamin C and soluble dry matter. The high values of total polyphenols and total flavonoid content indicate that orange peel is a rich source of bioactive compounds. While the antioxidant activity is highest in tiny-grade orange peels, naringin is highest in the peel of ruffled oranges. The study’s results are expected to improve the use of each grade of Sanh orange.