Based on the mode of formation of microsomal lipid peroxdation induced by Fe²⁺/cysteine and the principle of TBA reaction,a simple one-step microassay for the studying and screening of antioxidants in 96-wells plate was established. The comparative studies between the procedures in 96-wells plate and in test tube were also conducted.This microassay requires only small volume of diluted microsome and tested compounds,having the advantages of reliability,rapidness,simplicity and convenience. It is especially suitable for the pilot screening of antioxidants as well as the simultaneous study for many samples. This method can also be used to measure the lipid peroxidation induced by other systems.