Objective: To explore a approach of differentiating rapidly progressive central precocious puberty (RP-CPP) from slowly progressive central precocious puberty(SP-CPP) in girls. Methods: Girls showing breast development before 8-year-old were enrolled. On the first visit, the lutropin hormone（LH） and follicle-stimulating hormone（FSH） in serum were quantitatively detected by lutropin hormone releasing hormone（LHRH） stimulating test, LH and FSH in urine were tested by quantitative determination Kits. Among enrolled girls, fifty-three were diagnosed as central precocious puberty (CPP). The patients were divided into SP-CPP (30 girls) and RP-CPP (23 girls) groups after 6 month-follow-up for pubertal advancement, height acceleration, and bone age maturation. The levels of LH and FSH in serum and urine as well as related parameters were compared between RP-CPP and SP-CPP groups. Results: Serum LH peak, the ratio of LH peak/FSH peak (the ratio of LH/FSH peak) and urinary FSH(UFSH) level showed reference value in differentiating RP-CPP from SP-CPP, While morning urinary LH (ULH) and urinary FH/FSH ratio were not different between RP-CPP and SP-CPP girls. Compared with SP-CPP subjects, RP-PP ones had significantly increased serum LH peak [（18.06±3.68） IU/L vs. (7.58±2.50） IU/L, P<0.001] and serum LH/FSH peak ratio（1.67±1.08 vs. 0.97±0.43, P=0.014） and decreased UFSH[（4.34±1.52） IU/L vs. 7.60±1.20）IU/L, P=0.007]. The diagnostic efficacy of indices mentioned above were assessed with receiver operator characteristic （ROC） curve. It showed that the sensitivity and specificity of serum LH peak (cutoff 9.68 IU/L) for differentiating RP-CPP from SP-CPP were 76.9% and 87.0% respectively, and serum LH/FSH peak ratio (cutoff value 1.24) were 69.2% and 73.9%. Morning UFSH （cutoff value 5.91 IU/L）for prospectively diagnosing RP-CPP had a sensitivity of 76.9% and a specificity of 78.3%, which had similar efficacy as serum LH peak and serum LH/FSH peak ratio. Conclusions: Quantitative measurement of morning voided urinary gonadotropin is a noninvasive and reliable approach to diagnose RP-CPP prospectively, and UFSH measurement on the first visit has reference value in prospective diagnosis.