Abstract: To study the localization and mechanism of free radical production and injury by cadmium,we set up the toxical model by intravenous injecting cadmium chloride into rats.Then injury of hepatocytes and free radical(H₂O₂) localization were studied by electron microscopy,and contents of antioxidation were determinated.Results Showed H₂O₂ CeCl₃ positive precipitation on outer plasma membrane of hepatocytes first appeared at 1h after cadmium exposure,increased obviously at 3h and disappeared at 24h.Activities of antioxidase decreased clearly and with the serious in 3h(p<0.01),recovered progressively in 6h.But GSH content increased obviously before 3h(p<0.05),and decreased step by step.Conclusion:Free radical production is the important factor on injury of hepatocytes after cadmium exposure.