An ultrasonic height measuring instrument and a height correction method are provided. The instrument comprises an upright pole, an ultrasonic sensor locate at that top end of the upright pole and a standing platform located at the bottom end of the upright pole, wherein a marking pattern is arranged on the surface of the standing platform; at that top end of the upright pole, an image processor and a height corrector are also arranged; prior to testing, the mark pattern is photographed and a length change value between a line of interest in the obtained mark pattern and a standard mark pattern of interest stored in advance is calculated, whereby the height of the ultrasonic sensor to the surface of the standing platform is corrected according to the length change value. As that visual identification technology is introduced into an ultrasonic height measuring instrument, the absolute height of the upright pole is correct by utilizing a certain linear relationship between the change ofthe surface mark pattern information of the upright pole and the absolute height change of the upright pole in the image. By adopting the technical scheme, the error of ultrasonic height measurementcan be eliminated.