Well logging technology has been proved to be a reliable method to researching the rock mass structure and quality in hydropower project. In order to estimate the geological conditions and structural characteristics of rock mass, we took the south bank expansion project of Kariba power station as an example and carried out rock mass test at position Sd01, upstream cofferdam of water inlet and gate shaft of water inlet. By adopting acoustic and optical logging technology, we conducted in-site test and obtained the thickness of covering layer, weathering degree of bedrock, fissures development degree, and acoustic velocity of rock mass. The experimental results show that the water level at these places is 11.7, 13.1, 14.1-16.5 m,respectively, and average wave velocity is 3 200, 3 500, 2 000 m/s ,respectively,and the thickness of the covering layer is 21, 26 m, and above 30 m. Furthermore, the rock mass at Sd01 site and the gate shaft is relatively complete, with 12 and 11 fractures,whereas the rock mass of upstream cofferdam is broken and strongly weathered.