In order to solve the problem of precise investigation for deep-long tunnels in the ocean floor of the main channel of Shiziyang， the storage logging system was adopted to obtain parameters such as natural gamma， resistivity， well depth， well temperature， well inclination， etc. in the long reach scientific drilling hole （SZYSD-1S） with large horizontal displacement/vertical depth ratio in the main channel of Shiziyang. The logging data were correlated to accurately divide the rock （soil） properties of the formation； and the geological conditions of vertical holes and the horizontal hole were combined to accurately identify the hidden faults， and divide the surrounding rock level and weathering degree， and the permeability coefficient and permeability of the rock mass. A small-diameter geophysical logging evaluation method was established for deeply buried long tunnels （holes）. The results of SZYSD-1S hole test show that the logging response characteristics of the rock （soil） and the fault fracture zones of the Quarternary and Cretaceous strata are obviously different： the integrity coefficient of rock mass ranges from 6% to 82%， the rock mass quality falls into four levels from relatively complete to extreme fractured with the weathering degree four categories from full weathering to weak weathering， the permeability coefficient ranges from 1.01×10^-7 to 1.18×10^-3 m/s with the permeability from weak permeability to strong permeability. The logging evaluation results are basically consistent with the actual test results. This method is a necessary means to achieve accurate investigation for deep-long tunnels in the ocean floor， and effectively support the construction of the Guangdong-Hong Kong-Macao Greater Bay Area.