Abstract: Taking for example the ultrasonic logging imaging in one crossing engineering investigation of Yangtze River, and combined with other cases of high precise ultrasonic logging in China, then compared with traditional investigation technique and other logging imagings, this paper aims at analysising the advantage of new ultrasonic logging tool, such as in the aspect of the description of bedrock weathering zone and the estimation of rock quality designation. Especially in the aspect of precisely exposing rock fractures of underground rock mass structure, high precise ultrasonic logging imaging can provide large quantities of effective and apparent data rock mass around borehole, and these data are very good basis for the quantitative analysis of engineering design and point out one effective access to improve the technological level of geotechnical investigation, at the same time proving itself the most reliable method to expose trenchless underground rock mass structure up to now.