Objectives: The objective of this study was to investigate the antioxidant effects of manufactured Wen-pi-tang-Hab-Wu-ling-san (WHW$^{(R)}$) in vitro. Methods: WHW$^{(R)}$ was prepared by the pilot manufacture of WHW water extract from a GMP system appointed company. Antioxidative activities were determined by in vitro tests as follows: the scavenging activities of oxygen free radicals including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, superoxide anion, hydrogen peroxide and nitric oxide radicals, as well as ferrous ion chelating capacity and Trolox equivalent antioxidant capacity (TEAC). Results: WHW$^{(R)}$ significantly scavenged oxygen free radicals such as DPPH (IC$_{50}$=115.28 $pm$ 0.25 $mu$g/$mell$), superoxide anion (IC$_{50}$=8.56 $pm$ 0.08 $mu$g/$mell$), hydrogen peroxide (IC$_{50}$=240.36 $pm$ 3.41 $mu$g/$mell$) and nitric oxide (IC$_{50}$=162.28 $pm$ 0.21 $mu$g/$mell$) radicals. WHW$^{(R)}$ also showed ferrous ion chelating activity (IC$_{50}$=543.19 $pm$ 4.85 $mu$g/$mell$) and Trolox equivalent effects (IC$_{50}$=45.311 $mu$g/$mell$) in TEAC and ORAC assay, respectively. Conclusion: This study demonstrates that WHW$^{(R)}$ has strong antioxidative properties through free radical scavenging activity. These data suggest that WHW$^{(R)}$ be used as an antioxidant agent.