Backgrounds : Pomelo (Citrus grandis Osbeck) is the kind of citrus fruit which is Dicotyledoneae belongs to Rutaceae and special product in Jeju island. According to the previous researches, coumarin, eliocitrin, naringin are identified and these kinds of constituents revealed to be effective as anticancer, antioxidant, and antidiabetic. Until recently, there are many investigations about its functional properties were reported, but investigation about biological activities depend on extraction conditions are not sufficient. Methods and Results : 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was performed by the method of Blois with minor modification. After adding DPPH radical to each sample solutions, the mixtures were incubated in 30 minutes at aphotic place. Then, the degree of scavenging activity was recorded by microplate reader at 490 nm. The scavenging activity was expressed by RC50, which is the concentration of sample solution necessitated to scavenge 50% DPPH radical against negative control. For α-glucosidase inhibitory activity, the method using p-nitrophenyl-α-D-glucopyranoside (pNPG) was applied. To each samples, α-glucosidase and pNPG were mixed and incubated, consequently, Na2CO3 was added to terminate the reaction. Finally, absorbance was read at 450 nm. The same as DPPH radical scavenging activity, the inhibition was explicitly expressed by the amount of sample solution to inhibit 50% α-glucosidase, IC50. The 80% MeOH extract demonstrated the highest radical scavenging activity with 74.32±8.45 μg/ml. α-Glucosidase inhibitory activity was carried out to evaluate the inhibitory activity of sugar digestion and absorption and 60, 80% MeOH extract exhibited 416.35±11.07 μg/ml and 336.57±2.03 μg/ml, respectively. Conclusion : The DPPH radical scavenging and α-glucosidase inhibitory activity were evaluated in this study. The highest DPPH radical scavenging activity was seen in 80% Citrus grandis Osbeck MeOH extract, following 60% MeOH extract exhibited the second highest scavenging activity. Also, 80% MeOH extract showed 336.57±2.03 μg/ml, which was the highest α-glucosidase inhibition among all extracts.