Purpose: Various antioxidants in serum, recognized as reductants,are capable of reducing a ferric tripyridyltriazine (Fe3+-TPTZ) toits corresponding Fe2+-TPTZ complex which exhibits a maximum absorption at 593 nm. Based on this premise, a direct assessment ofthe total antioxidative capacity (TAC) of serum has been developed and automated using a chemistry autoanalyzer. Method: The Olympus AU600 Chemistry Autoanalyzer was used.The automated procedure has the following analytical parameters:Pipettor setting are: reaction mode二end point; wavelength = 600 nM,temperature=37℃，absorbance reading number=27; interval=18sec. Results:The assay performed under our optimum condition has excellent precision data, with within-run and day-to-day reproducibilities (expressed as CVs) of three control levels were all below 3％. The recovery studies revealed an average of 101.4 1.7%. The stability studies revealed that specimens stored at 4 ℃ could maintain stability for only 3-day. The linearity of the assay extends from 0.025to 1.2 mmol/L Trolox equivalent unit(TEU). The established normal reference range is 0.75 0.12 TEU (N=891). The proposed TAC assay hasa throughput of >300 test/hr. Clinical utilities were exemplified by the assessment of the TAC values on various groups of oxidative stress-related diseases and their TAC values were all significantly lower thanthe normal reference controls (p<0.001). Conclusion: Our proposed microassay for the TAC measurement has been shown to be simple, rapid and clinical useful in identifying individuals who may be suffering from oxidative stress and eventually be rescued by consuming hydrogen-rich water or inhaling hydrogen gas.