At Ras-Suder Research Station, South Sinai, Desert Research Center, two field experiments were conducted during summer seasons of 2012 and 2013. The main object of this research was improving the productivity of sweet pepper plant (Capsicum annuum L.) hybrid "Sonar" using some antioxidant treatments on fruit quality and chemical constituents of fruits. Aqueous solutions of antioxidants as foliar spray; i.e., ascorbic acid (Vitamin C), Oxalic acid, Salicylic acid (SA), and Tocopherol (Vitamin E) within four different concentrations of these antioxidants (0.0, 200, 400 and 600 ppm) were applied at 20, 40 and 60 days after transplanting. Obtained results indicated  that the best antioxidant treatments which gave the highest values of fruit quality (V.C, T.S.S, fruit size, fruit length, diameter and shape) and chemical content (N, P, K, Ca, Mg and carbohydrates) were spraying sweet pepper plants with salicylic acid followed by ascorbic acid with 400 ppm of both antioxidants.