Fermented products, dried mycelia broth, and mycelia-free broth of Laetiporus sulphureus submerged cultures were extracted with ethanol and hot water under optimal culture conditions and investigated for their antioxidant properties. Ethanolic extracts from dried mycelia broth (EEM) and mycelia-free broth (EEB) and hot water extracts from dried mycelia (HWEM) show extraordinary antioxidant properties for all EC50 values below 10 mg/mL except for EEM, as measured by the scavenging effects on DPPH radicals and chelating effects on ferrous ions. Ascorbic acid is rich in EEB and α-tocopherol, and total flavonoids are abundant in EEM. Total phenols are mainly found in EEB and HWEM. There is a high correlation between total phenol content and EC50 values. The correlation coefficient (R2) of the reducing power is 0.994; the R2 of the scavenging effect on DPPH radicals is 0.992; the R2 of the chelating effects on ferrous ions is 0.949; and the R2 of the scavenging effect on superoxide anions is 0.995. These results suggest that extracts of L. sulphureus fermented products are of considerable application potential in antioxidant-related pharmaceutical industries.