Extra virgin olive oil is so expensive which makes tempting to adulterate them with other lower price vegetable oils to achieve more profit. The aim of this study is to develop a simple, direct, and reliable UV-spectrophotometric procedure for identification and quantification of the adulteration of pure Syrian kaissy olive oil (SKOO) with sunflower oil (SO). A simple procedure has been developed for detection, classification and quantification of the adulteration of pure Syrian kaissy olive oil (SKOO) with sunflower oil (SO). The oxidative degradation was investigated by UV-visible spectroscopy and used to monitor the changes using peroxide values. The results indicated that the K232 (2.31), K270 (0.38), and ΔK (0.01) values of genuine SKOO, which are lower than the 2.5, 0.22 and 0.01, the maximum values established by the national and international regulations for extra virgin olive oil. The obtained results demonstrated the increase in the adulteration percentage increased the K232, K270 and ΔK values the values of K232, K270 and ΔK values in SKOO mixtures with SO. The concentration of the adulterant of sunflower oil in olive oil showed a positive correlation with K232 (R2 = 0.9886; p< 0.01), K270 (R2 = 0.9984; p< 0.01) and ΔK (R2 = 0.9992; p< 0.01). Equation to predict percent of adulteration from K232, K270 and ΔK values were developed. The obtained results demonstrated the feasibility of detecting adulterations of SKOO with SO.