Objective Evaluate the diagnostic value of the pelvic ultrasound in girls of central precocious puberty（CPP）. Methods 219 cases of girls with early breast development who visited our clinic the first time were selected，the girls were divided into CPP group(128 cases) and simple breast development（premature thelarche，PT 91 cases） group according to the gonadotropin-releasing hormone stimulation test（GnRHa，A peak LH concentration of at least 5 IU/L was classified as CPP）. Morphometric parameters of both groups by pelvic ultrosonography were measured and compared separately：uterine length，width，thickness and volume，ovarian length，width，thickness and volume，diameter of the maximal follicle．Correlation analysis was made between ultrasonic parameters and GnRHa test.The optimum cutoff values were confirmed through area under the receiver operating characteristic curve（ROC）.Results Compared with the PT group ,the uterine length，uterine volume，ovarian length，ovarian volume and the diameter of maximal follicle were significantly larger in the CPP group[（2.51±0.43）cm vs.（1.93±0.29）cm，（1.86±1.08）ml vs.（1.06±0.51）ml；（2.58±0.50）cm vs.（2.02±0.51）cm；（1.81±1.09）ml vs.（0.98±0.46）ml；（0.67±0.17）cm vs.（0.21±0.12）cm）].The difference was statistically significant (P < 0.05) .The morphometric parameters above were significantly associated with LH peak in CPP girls, and no correlation with PT girls.The areas under ROC curve of uterine length，uterine volume，ovarian length，ovarian volume and diameter of maximal follicle respectively were 0.70，0.81，0.59，0.63，0.88 in girls of CPP.Conclusion The pelvic ultrasound parameters are certain valuable in the diagnose of girls with CPP，especially the uterine volume and diameter of maximal follicle.