Objective To investigate the association of low serum level of indirect bilirubin with cerebral hemorrhage transformation after thrombolysis in patients with stroke.Methods A total of 175 patients with acute ischemic stroke who underwent intravenous thrombolysis in our hospital from December 2016 to October 2019 were enrolled and divided into cerebral hemorrhage transformation group with 12 patients and non-cerebral hemorrhage transformation group with 163 patients； 200 individuals who underwent physical examination during the same period of time and had healthy results were enrolled as control group. The levels of total bilirubin， direct bilirubin， and indirect bilirubin were measured for all subjects before thrombolysis. A multivariate logistic regression analysis was used to investigate the influencing factors for the development of cerebral hemorrhage transformation after thrombolysis in patients with ischemic stroke.Results The ischemic stroke group had significantly higher serum levels of total bilirubin and indirect bilirubin than the control group （P<0.05）. Compared with the non-cerebral hemorrhage transformation group， the cerebral hemorrhage transformation group had significantly higher incidence rates of atrial fibrillation and massive cerebral infarction， diastolic pressure before thrombolysis， and National Institutes of Health Stroke Scale （NIHSS） score （P<0.05）. Before thrombolysis， the cerebral hemorrhage transformation group had significantly lower serum levels of total bilirubin and indirect bilirubin than the non-cerebral hemorrhage transformation group （P<0.05）. The multivariate logistic regression analysis showed that high NIHSS score and low indirect bilirubin were risk factors for cerebral hemorrhage transformation after thrombolysis in patients with ischemic stroke.Conclusions Low serum indirect bilirubin is negatively correlated with the prognosis of patients with ischemic stroke after thrombolysis， and low indirect bilirubin is a risk factor for cerebral hemorrhage transformation after thrombolysis in patients with ischemic stroke.