Aim To observe the change of thrombomodulin and its relationship with tumor necrosis factor-α(TNF-α)in acute cerebral infarct with hospital acquired pneumonia(HAP). Methods The patients with acute cerebral infarct were divided into pure infarct group(n=24),and acute infarct with HAP group(n=16),compared with normal control group(n=13).The serum samples were obtained from 1 d to 21 d after infarct.The serum level of thrombomodulin and TNF-α were examined by enzyme-linked immunosorbent assay(ELISA) method and radioimmunoassay respectively. Results The serum levels of thrombomodulin of acute infarct with HAP group were significantly lower than those of pure infarct group in the first week and 14 d after infarct(p<0.05),with similar result at 21 d.The serum levels of TNF-α of acute infarct with HAP group were significantly higher than those of pure infarct group from the first week to 21 d after infarct(p<0.05),although HAP had been prohibited in 21 d.In the group of acute infarct with HAP the serum levels of thrombomodulin were related inversely with that of TNF-α.The relationship between thrombomodulin and TNF-α compromised with Gompertz curve. Conclusions It's possible that the increase of serum TNF-α in acute infarct with HAP may injury the endotheliocyte of brain vessel and prohibited the anticoagulative system,presenting with downregulation of the level of serum thrombomodulin.