Objective To evaluate the correlation between fetal adrenal artery Doppler velocimetry parameters and onset time of labor. Methods The objects were those who underwent Doppler velocimetry ultrasound during 39 weeks of pregnancy with followed-up labor outcomes. The objects without spontaneous delivery and need artificial intervention till after 41 weeks were considered as prolonged pregnancy. The objects without spontaneous delivery before 41 weeks were considered as control. The pulsatility index (PI), resistance index (RI) and systole/diastole (S/D) of fetal adrenal between two groups were compared. ROC curve was established to evaluate the efficiency of adrenal artery Doppler velocimetry parameters to predict prolonged pregnancy. Results The adrenal artery Doppler velocimetry parameters were successfully measured in 177 pregnant women, the success rate was 88.5% (177/200). Among them there were 53 pregnant women in the prolonged pregnancy group and 124 pregnant women in the control group. The mean PI and RI of the fetal adrenal artery in prolonged pregnancy group were 1.89±1.1 and 0.81±0.19, respectively. The mean PI and RI of the fetal adrenal artery in control group were 1.47±0.38 and 0.72±0.09, respectively. There were statistically significant difference of PI and RI between the prolonged pregnancy and control group (P＜0.05). The area under the curve (ACU) of the PI in prolonged pregnancy group was 0.665 (95%CI: 0.511-0.820, P=0.039) and the RI was 0.679 (95%CI: 0.533-0.825, P=0.022). The best cutoff values of PI and RI for predicting prolonged pregnancy were 1.65 and 0.78, respectively. The sensitivity, specificity, PPV, NPV and accuracy of PI and RI were 71.1%、70.6%、86.5%、48.0%、71.0% and 61.5%、77.8%、66.7%、73.7%、71.0%, respectively. Conclusion Fetal adrenal artery Doppler velocimetry is associated with onset time of labor. The PI and RI in prolonged pregnancy women are higher than that of control group, the fetal adrenal artery Doppler velocimetry can be used to predict the prolonged pregnancy.