Objective: To evaluate the level of first morning voided (FMV) urinary luteinizing hormone (LH) in girls with breast development, and to determine the value of FMV urine LH in the evaluation of central precocious puberty (CPP). Methods: From September 2018 to April 2021, among the patients who were admitted to the Department of Pediatrics of Peking University Third Hospital for "precocious puberty" and underwent gonadotropin-releasing hormone (GnRH) stimulation test, a total of 108 girls were enrolled. According to CPP diagnostic criteria, they were divided into CPP group (n=45) and non-CPP group (n=63). The clinical characteristics and hormone levels of the two groups were compared. Receiver operating characteristic (ROC) curve was used to analyze the cut-off value of FMV urinary LH in the diagnosis of CPP in girls. Further analyses were done to evaluate the value of FMV urinary LH in the diagnosis of CPP using correlation analysis between urinary LH level and common clinical cha-racteristics. Results: ROC curve analysis showed that FMV urine LH level was significant for the diagnosis of CPP. The cut-off value of FMV urine LH was 0.69 IU/L (specificity 56.9%, sensitivity 85.0%, area under curve 0.804, P < 0.001). The basic clinical characteristics without GnRH stimulation test were analyzed by binary Logistic regression analysis, indicating that the level of FMV urine LH, uterine volume, ovarian volume and advanced T-bone age had predictive significance for CPP diagnosis in girls (OR values were 2.125, 1.961, 1.564 and 2.672, respectively). The prediction model was established and the area under the ROC curve was 0.904, P < 0.001. The level of FMV urine LH was positively correlated with the levels of serum LH, FSH and estrogen before GnRH stimulation test, the peak value of blood LH after GnRH stimulation test, T bone age and uterine volume, with r values of 0.462, 0.373, 0.242, 0.360, 0.373 and 0.263, respectively, and P values were < 0.001, < 0.001, 0.013, < 0.001, < 0.001 and 0.007, respectively. Conclusion: FMV urine LH can provide a good indication for the diagnosis of CPP. Combining with bone age advanced level and pelvic ultrasound measurement, the predictive value of FMV urine LH can be further improved for the diagnosis of CPP in girls.