The method of positioning a Doppler ultrasound transducer for performing blood flow measurement according to the invention comprises the steps of: detecting a pressure oscillation signal from an inflated cuff placed on patients artery detecting an ultrasound pulse signal from the Doppler ultrasound transducer placed along the artery deriving a first signal from the pressure oscillation signal and the ultrasound pulse signal, the first signal indicating the degree of synchronization between the pressure oscillation signal and the ultrasound pulse signal and outputting an indication signal to indicate the Doppler ultrasound transducer is in a desired position when the first signal satisfies a predefined condition. Since the synchronization property of the cuff pressure oscillation signal and the ultrasound signal caused by the blood flow is utilized to determine whether the transducer is well positioned or not, ultrasound signal, which is a pulse signal but not reflecting the blood flow of the artery, could be determined as not in synchronization with the oscillation signal and therefore the accuracy of the positioning could be improved.
