Abstract: Objective:To explore the application value of serum level of ubiquitin carboxyl-terminal esterase L1(UCH-L1) in the diagnosis of hypoxic-ischemic encephalopathy in newborn rats.Methods:One hundred and sixty eighty newborn SD rats were randomly divided into the control group,sham-operation group and hypoxic-ischemic brain damage(HIBD) model group(56 rats each group).Each group was randomly subdivided into the 6 h,12 h,24 h,48 h,72 h,96 h and 7 d groups(8 rats each subgroup).The HIBD model was established using the improved Rice method.All rats were sacrificed to obtain blood at different time points.The serum levels of UCH-L1 were tested by ELISA.Results:At different time-points,the differences of the levels of UCH-L1 between three groups were statistically significant(P<0.01),the levels of UCH-L1 in HIBD model group were significantly higher than that in control group and sham-operation group(P<0.01),and the difference between the control group and sham-operation group was not statistically significant(P>0.05).The differences of the levels of UCH-L1 in HIBD model group between different time-points were statistically significant(P<0.01).In HIBD model group,the serum levels of UCH-L1 began to significantly increase at 6 h,reached the peak value at 48 h,then decreased gradually.The more severe the brain damaged,the higher the level of serum UCH-L1 was.Conclusions:The levels of UCH-L1 is positively correlated with the severity of the brain damage.The expression of UCH-L1 can be used an indicator in evaluating the brain damage.