In the soil-rock mixed areas where the soils overlie on the rock layer, the rock-socketed retaining piles have been widely used for deep excavations. Up to date, little attention has been paid to performance of the rock-socketed piles used for deep excavation. Therefore, using the two-dimensional finite element program, Plaxis2D, a typical deep excavation engineering supported by rock-socketed piles with the whole embedded portion in rock is analyzed to investigate behavior of the rock-socketed retaining piles in detail. Computation results have shown that for rock-socketed retaining piles used in deep excavations, there exists an ultimate or a maximum rock-socketed depth which can be estimated by the pile diameter. For the ultimate rock-socketed depth, in the final excavation step, the first zero bending moment point of the rock-socketed part of the pile generally locates near the top surface of the rock layer. When the excavated surface is located at the top surface of the rock layer, the corresponding shear force distribution of the rock-socketed pile has an extremum at the same position.