Objective To analyze the relationships between color Doppler ultrasound parameters and insulin sensitivity index ( ISI ) and clinical efficacy in rats with polycystic ovary syndrome ( PCOS ) combined with hyperinsulinemia (HI). Methods A total of 140 3-week-old female SD SPF-grade rats were divided randomly into a PCOS without HI model (control group, n=70) and a PCOS combined with HI model (study group, n= 70). After successful modeling, we used color Doppler ultrasound to detect the physical indicators, hemodynamic indicators, and ultrasound features of rat ovaries, and draw venous blood to evaluate ISI. Rats in the study group were treated with metformin by intragastric administration. The color Doppler ultrasound parameters of the good-effect and the pooreffect group were compared and a receiver operating characteristic curve (ROC) was drawn to analyze the value of the color Doppler ultrasound parameters for evaluating the curative effect of metformin in rats with PCOS combined with HI. Results The total ovarian area (TA), ovarian volume (OV), ovarian interstitial area (SA), vascularization index (VI), blood flow index (FI), fasting insulin (FINS), and fasting blood glucose (BFG) of the research group were all greater than those of the control group, while the resistance index, pulsatility index and ISI were observed significantly lower compared with contrast, there were obvious difference (P<0. 05). The color Doppler ultrasound parameters TA and SA were negatively correlated with ISI ( r= - 0. 501, r= - 0. 492, respectively, P< 0. 05), and ovarian RI and PI were positively correlated with ISI (r= 0. 504, r= 0. 485, respectively, P<0. 05). TA, OV, SA,VI, FI, VFI, PSV, PDV, low-density lipoprotein cholesterol, FPG, FINS, LH, and FSH were all significantly lower while RI and PI were significantly higher in the good-curative-effect group compared with the poor-curative-effect group (all P<0. 05). According to ROC curve analysis, the sensitivity and specificity of color Doppler ultrasound parameters combined with clinical efficacy were 90. 9% and 90. 2%, respectively, and the area under the curve (AUC) was 0. 901. Conclusions Color Doppler ultrasound parameters are closely related to ISI and therapeutic efficacy in rats with PCOS combined with HI, and may thus predict clinical efficacy in patients with these conditions.