Summary: The changes of tumor necrosis factor-α (TNF-α) and brain ultrastructure during cardiopulmonary resuscitation and the effects of ulinastation injection were observed, and the mechanism was investigated. Twenty-four adult healthy Sprague-Dawley rats were randomly divided into.control group (8 rats), resuscitation group (8 rats) and ulinastatin (UTI) group (8 rats). Rats in control group underwent tracheotomy without clipping the trachea to induce circulatory and respiratory standstill. Rats in resuscitation and ulinastatin group were subjected to the procedure of establishing the model of cardiopulmonary cerebral resuscitation (CPCR). Rats in ulinastatin group were given with UTI 104 U/kg once after CPCR. In the control group, the plasma was collected immediate,30 min, 2 h, 4 h, and 6 h after tracheotomy. In resuscitation group and UTI group, plasma was collected immediate after tracheotomy, 30 min, 2 h, 4 h and 6 h after successful resuscitation. The plasma levels of TNF-α were determined by radioimmunoassay (RIA). At the end of the experi-ment, 2 rats were randomly selected from each group and were decapitated. The cortex of the brain was taken out immediately to observe the ultrastructure changes. In control group, there were nosignificant differences in the level of TNF-α among different time points (P＞0.05). In resuscitation group, the level of TNF-α was increased obviously after resuscitation (P＜0.01) and reached its peak 2 h later after resuscitation. An increasing trend of TNF-α showed in UTI group. There were no differences in TNF-α among each sample taken after successful resuscitation and that after tracheotomy. The utrastructure of brains showed the injury in UTI group was ameliorated as compared with that in resuscitation group. In early period of CPCR, TNF-α was expressed rapidly and kept increasing. It indicated that TNF-α might take part in the tissue injury after CPCR. The administration of UTI during CACR could depress TNF-α and ameliorate brain injury. By regulating the expression of damaging mediator, UTI might provide a protective effect on the tissue injury after CPCR.