Objective To calculate and measure the depth and radius of the target vessel in the upper limb venous ultrasound image in order to contribute to automatic venipuncture.Methods Two methods of measuring the radius of veins in an ultrasonic vein cross section image were adopted.One method was to segment the vein based on the threshold selected after evaluation, and then scan the upper and lower edges of the vein to obtain the radius.The other method was based on Otsu method,which was to divide the vein and then morphologically process the binary image.The radius was calculated in a manner similar to the first method.After the radius was obtained, the depth of the vein was corrected in conjunction with the radius.Results The above two methods were tested on 500 upper limb venous ultrasound images.The accuracy rate of the first method was 93.0%, and that of the second method was 99.4%.Conclusion The method based on Otsu and morphological processing is more effective for radius measurement of veins in upper limb venous ultrasound image.