The aim of this study was to investigate the antioxidant activities of various parts (barks, buds, and leaves) of Cinnamomum cassia extracted with ethanol and supercritical fluid extraction (SFE). For the antioxidant activity comparison, IC50 values of the SFE and ethanol extracts in the DPPH scavenging assay were 0.562-10.090 mg/mL and 0.072-0.208 mg/mL, and the Trolox equivalent antioxidant capacity (TEAC) values were 6.789-58.335 mmole Trolox/g and 133.039-335.779 mmole Trolox/g, respectively. In addition, the total flavonoid contents were 0.031-1.916 g/ 100 g dry weight of materials (DW) and 2.030-3.348 g/ 100 g DW, and the total phenolic contents were 0.151-2.018 g/ 100 g DW and 6.313-9.534 g/ 100 g DW in the SFE and ethanol extracts, respectively. Based on the results, the ethanol extracts of Cinnamon barks have potential value as an antioxidant substitute and this study also provide a better technique to extract the natural antioxidant substances from C. cassia.