The antioxidant activity of synthetic antioxidants, BHA, BHT and TBHQ and natural antioxidants, rosemary extract, sesamol, caffeic acid and pyrogallol In a skip jack oil were studied. A control and substrates containing synthetic(0.02%) and natural antioxidant (0.05%) were stored in an incubator kept at 37$^{circ}C$ for 8 days. The antioxidant activity of synthetic and natural antioxidants was investigated by comparing peroxide values. The results of this study were as follows All the synthetic antioxidants used for this study exhibited antioxidant activity in skip jack oils. The antioxidant activity of TBHQ was greater than that of BHA and BHT. The rosemary extract did not show antioxidant activity in skip jack oils. The antioxidant activity of sesamol and caffeic acid were greater than those of BHA. Especially Pyrogallol exhibited very strong antioxidant activity, comparable to that of the TBHQ. The antioxidant activity of the sesamol, caffein acid and pyrogallol used skip lack oil, In decreasing order as follows : pyrogallol>caffeic acid> sesamol.