Abstract: OBJECTIVE To establish a new bioactivity assay method for the quality control of Qingkailing injection based on its effect of ameliorating oxidative stress in treating cerebral stroke. METHODS Four bioactivity indicators including investigating the activity of Qingkailing injection on scavenging superoxide anion radical, hydroxy radical and DPPH radical along with its total antioxidant capacity were assessed. Among these, the total antioxidant capacity assay with the best linearity and sensitivity was selected for further methodological investigation, and then applied to compare the quality of three batches of Qingkailing injections. RESULTS Total antioxidant capacity assay possessed the best linearity and sensitivity compared with the other 3 methods. Following methodological investigation exhibited that its intra- and inter-day precision, stability were also conformance to requirements. The biological qualities of three batches' samples, which was represented by the concentration of trolox with equivalent activity, were similar without statistical difference. CONCLUSION The total antioxidant capacity assay is suitable for evaluating the quality of Qingkailing injection in its clinical applications associated with the antioxidant capacity, such as cerebral stroke, etc. This method also serves as a beneficial supplement for the current quality control mode.