The present study was conducted on the orange peel (OP), mandarin peel (MP) and lemon peel (LP) to evaluate its bioactive compounds and use it in some vegetable oils and some functional foods. The total phenolics content in OP, MP and LP were 818.86, 996.8 and 956.86 mg / 100 g, respectively and total flavonoids content in OP, MP and LP were 476.56, 517.38 and 406.23 mg / 100 g, respectively. Also, the amount of essential oils in OP, MP and LP were 2.4, 1.9 and 0.87 %, respectively. The three citrus peels, OP, MP and LP had a reasonable amount of neutral dietary fiber (NDF) and acid dietary fiber (ADF) (17.85, 21.83 and 12.43 % and 13.52, 10.94 and 11.32 %, respectively). It is clear that the by-product of food processing industries has added value by identifing and isolating of their bioactive compounds. Two analytical methods were used to determine their antioxidant activity 2, 2- diphenyl-1- picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP). IC50 were 6.59, 7.49 and 22.69 mg / ml for OP, MP and LP, respectively. The absorbance of OP, MP and LP in the FRAP method were 0.34, 0.52 and 0.56, respectively. The oxidative stability of palm olein, soybean and sunflower oils containing each of OP, MP and LP and their extracts as novel sources of antioxidants versus butylated hydroxytoluene (BHT) as a synthetic antioxidant were also studied and evaluated by measuring their induction periods (IPs) using the Rancimat method. The ethanolic extracts of the peels were added at two levels; 1000 and 2000 ppm, individually, while the aforementioned whole peels (OP, MP and LP) were added in different quantities according to its extract yield percentage. Moreover, the three citrus peels were added to some functional foods such as cookies and pasta in different concentrations.