The boiling process caused decrease from 22.22 mg/100 g to 3.01 mg/100 g in total phenolic content of celery root. Similarly, after boiling process, antioxidant activity of sample reduced from 2.67% to 0.53%. The main phenolic compounds of celery were found as catechin (50.93 mg/100 g), 3,4-dihydroxybenzoic acid (39.81 mg/100 g), 1,2-dihydroxybenzene (35.19 mg/7100 g), and gallic acid (19.21 mg/100 g), respectively. Generally, the reduction in phenolic compounds was observed with boiling process. The highest reduction was determined in 3,4-dihydroxybenzoic acid from 39.81 mg/100 g to 30.62 mg/100 g. Additionally, gallic acid and quercetin contents of celery decreased from 19.21 mg/100 g to 15.75 mg/100 g and from 17.28 mg/100 g to 13.08 mg/100 g, respectively, while catechin content of sample increased from 50.93 mg/100 g to 54.77 mg/100 g after boiling process. A significant decrease in the total phenol and antioxidant activity values of boiled samples was observed. Practical applications: Celery is a rich source of natural active compounds having different biological properties and mechanism of action. The boiling process impacts the physical and chemical properties and bioavailability of functional compounds in vegetables. Most of the vegetables are cooked by boiling in water before consumed. This cooking process would bring about a number of changes in physical and chemical characteristics of vegetables. The present research was carried out for evaluation effects of antioxidant capacity, total phenolic, and phenolic compounds of the celery root by boiling cooking method compare to fresh.