Objective To study the method of gray-scale blood flow imaging and image processing in condition of high frequency ultrasound,and the implementation of the system.Methods On the base of research of scattered signals of red blood cells in high frequency ultrasound,20 MHz ultrasound mechanical and linear scanning probe was used to transmit a number of pulses on a scan line.Pulse-echo subtraction method was used to obtain the blood flow information.At the end,simulated blood vascular was used to conduct flow imaging,and the obtained images were analyzed.Results Experiment results showed that clear blood flow images were obtained using this system.The noise from perivascular tissue could be filtered and the signals from blood flow could be enhanced after image processing.Conclusions In the detection of superficial blood vessel,blood flow signals can be obtained even using single pulse emitting via high frequency ultrasound.The blood flow imaging system can be implemented after image processing.