The present disclosure relates to medical monitoring and provides a method and an apparatus for detecting an instantaneous fetal heart rate of a Doppler fetal heart sound based on time-frequency analysis. The method comprises: pre-processing a Doppler fetal heart sound using a band pass filter applying time-frequency analysis to the pre-processed ultrasound Doppler fetal heart sound, so as to obtain a time-frequency graph of the ultrasound Doppler fetal heart sound by STFT for simple and fast calculation applying a cross correlation method to obtain an instantaneous of the fetal heart sound by: selecting a characteristic band from the time-frequency graph of the Doppler fetal heart sound, selecting a characteristic template based on a priori knowledge of the heart sound signal, calculating a cross-correlation function between the characteristic band and the characteristic template to plotting a cross correlation curve and calculating an instantaneous heart rate of the ultrasound Doppler fetal heart sound signal by calculating intervals between peaks of the cross correlation curve. According to the present disclosure, the instantaneous heart rate of the ultrasound Doppler fetal heart sound signal as collected clinically can be calculated with a simple method and has a fast operation speed and a high accuracy.
