Aims: The impacts of low concentration carbohydrate of preoperative oral rehydration solution were investigated on perioperative stress in patients undergoing sagittal split ramus osteotomy (SSRO). Methods: The randomized intervention clinical trial was performed. The subjects were divided into three groups by preoperative oral ingestion: ORS groups; low concentration carbohydrate beverage (2.5%), HCHO group: low penetration pressure high concentration carbohydrate (12.5%) drink before entrance, MW groups: mineral water. Oxidative stress (d-ROMs), antioxidant potentials (BAP), cortisol, and insulin resistance (HOMA-IR) were measured at six points: entrance, after osteotomy, wound closure, the first postoperative day, third day, and the starting day of oral ingestion. Results: A total of 25 patients were enrolled. At the time of wound closure, values BAP in ORS group and HCHO group did not drop, but that in MW group did. The values of d-ROMs and cortisol during surgery were lower. The values of d-ROMs in the postoperative measuring phrase rose above the standard zone. However, there were no significant differences among the groups. The maximum value of HOMA-IR in MW group was at the third postoperative day, but there were no significant differences among the groups. Conclusion: It is suggested that preoperative oral rehydration solutions containing of low concentration of carbohydrate could prevent the deterioration of antioxidant potentials during surgery in patients undergoing SSRO. However, surgical stress of SSRO was considered not to be strong enough to affect d-ROMs, cortisol, or HOMA-IR. Keywords: preoperative oral rehydration solution, carbohydrate, perioperative stress, SSRO