Saururus chinensis, a core member of Saururaceae, is an important herbal medicine used in traditional Chinese and Korean medicine to treat human diseases. Sauchinone and manassantin B, lignans from Saururus chinensis, is a diastereomeric lignin with numerous pharmacological applications in medicine, including antioxidant, anti-inflammatory, anti-apoptotic, anti-obesity, and hepatoprotective effects. In this study, we aimed to determine the antioxidant effect of the ethanol extract of Saururus chinensis and to establish the optimal extraction method using HPLC. Saururus chinensis extract (SCE) was prepared by using various extraction methods and solvents. The crude extracts were then subjected to a fractionation process to obtain different fractions. Antioxidant effects of SCE, fractions and  major compounds (sauchinone and manassantin B) were assessed by ROS and ONOO^- scavenging assay. The contents of major compounds in SCE were analyzed using HPLC. Based on these results, an optimal extraction method was established that yielded the highest content of the major components. The antioxidant assays confirmed that all extracts, fractions, and major compounds exhibited significant antioxidant activity. Furthermore, both sauchinone and manassantin B showed strong antioxidant effects, indicating that they are the primary active components of SCE. Quantitative analysis by HPLC revealed that the highest concentrations of the major compounds were obtained from reflux extraction using 100% ethanol. Consequently, this method was determined to be the optimal extraction condition. In the fractionation process, sauchinone was measured to be most abundant in the hexane fraction, whereas manassantin B was found in the highest concentration in the DCM fraction. In conclusion, the potent antioxidant effects of Saururus chinensis is largely attributable to the high content of the major lignans, sauchinone and manassantin B, with the optimal extraction method identified as refluxing with 100% ethanol.