One of the main effective factors on olive oil quality is harvesting fruit at proper time. In this study, the effect of fruit harvesting time on oil antioxidant compounds of four olive cultivars, Zard, Rowghani, Arbequina and Coratina was investigated at Roodbar region, Guilan province. Therefore, the characteristics such as total chlorophyll, total carotenoid, total phenol, total flavonoid, antioxidant capacity, IC₅₀ and anti-radical efficiency (AE) were determined in the oil. The results showed that with delaying in harvest time, antioxidant compounds of olive oil such as total chlorophyll and carotenoid, total phenolic and flavonoid decreased, that followed by declining oil antioxidant capacity and AE and, but increasing IC₅₀. The results also showed that there was a positive significant correlation between olive oil total antioxidant activity with AE (+0.919), total chlorophyll (+0.562), total carotenoid (+0.562), total phenolic (+0.86) and flavonoid (+0.868) and a negative correlation with IC₅₀ (-0.87). Overall, the highest antioxidant compounds were found when Zard, Rowghany and Arbequina cultivars fruits were harvested from 7 October to 18 October and 18 october to1 November for Coratina cultivars. Furthermore, delaying in fruit harvest time could increase olive oil content but declined oil antioxidant compounds and its nutritional value.