Objective. To study the diagnostic value of combined detection of pelvic ultrasound and serum LH, FSH, and E2 levels in children with idiopathic central precocious puberty (ICPP). Methods. 30 cases of children with ICPP admitted to our hospital from January 2019 to January 2021 were selected as the experimental group, and 30 healthy people during the same period were selected as the control group. Both groups received pelvic ultrasound and serum LH, FSH, and E2 detection; the two groups were compared in terms of serum indicators, combined diagnosis, specificity, and sensitivity. Results. There were statistical differences in height, leptin, bone age, and areola diameter between the two groups (p < 0.05). The length of the uterus, the volume of the uterus, the area of the ovary, the volume of the ovary, and the maximum diameter of the follicle in the experimental group were larger than those in the control group (p < 0.05). The endometrial thickness of the experimental group was significantly greater than that of the control group (p < 0.05). The levels of serum LH, FSH, and E2 in the experimental group were significantly higher than those in the control group (p < 0.05). The area of the combined detection was significantly larger than that of the single detection. The combined detection was superior to the single detection with respect to the area, standard error a, asymptotic Sig. B, and asymptotic 95% confidence interval (p < 0.05). The sensitivity of the combined detection was significantly higher than that of the single detection. Conclusion. The combined detection of pelvic ultrasound and serum LH, FSH, and E2 levels may be a preferred technique for the diagnosis of children with ICPP due to its benefits of high sensitivity and accuracy. It is worthy of clinical promotion and application.