Objective To explore the effect and importance of increasing Doppler ultrasound frame frequency on measuring peak systolic velocity (PSV) and pulsatility index (PI) of middle cerebral artery (MCA). Methods The blood flow spectrum of 659 normal fetal middle cerebral artery (MCA) during 22-40 weeks of gestation was measured by color Doppler ultrasound. The parameters of blood flow were measured: peak systolic velocity (PSV) and pulsatility index (PI). The first measurement of MCA (MCA.g) was performed under the routine setting of ultrasound equipment.The second measurement of MCA (MCA.o) is carried out under the condition of improving the frame rate by optimizing the setting, and the two measurement results of MCA blood flow parameters are compared.Results The PSV, PI value and frame frequency of MCA.o optimized setting were significantly higher than those of MCA.g conventional setting (P < 0.001). CONCLUSION Compared with conventional ultrasound measurement technology, optimizing Doppler ultrasound settings and increasing frame frequency can improve the PSV and PI values of fetal MCA blood flow parameters. It plays an important role in the evaluation of prenatal fetal circulation system. It is worth further clinical study and adjusting the reference value of the current normal range of MCA blood flow parameters.