The utility model relates to the technical field of bridge pile foundation construction, in particular to a guide support for a cast-in-situ bored pile. The device comprises a pile casing, a positioning frame and a guide pipe, wherein the positioning frame is mounted on the top surface of the pile casing, the positioning frame is of a square frame body structure, the center of the positioning frame is distributed on the central axis of the pile casing, and a guide hole which penetrates through the frame edges in the vertical direction is formed in the middle of each frame edge of the positioning frame; the number of the guide pipes is four, the guide pipes are inserted into the guide holes in an aligned mode in the vertical direction, the hole diameters of the guide holes are matched withthe outer diameters of the guide pipes, the upper ends of the guide pipes are hung on the guide holes, and the lower ends of the guide pipes penetrate through the pile casing and then extend downwardsto be distributed in the pile holes. Through the cooperation of the pile casing, the positioning frame and the guide pipe, the problems that the top of the reinforcement cage deflects to cause non-uniformity of a protective layer and reinforcement leakage of the reinforcement cage are effectively solved, the reinforcement cage is prevented from scratching a mud protection wall, and meanwhile, thereinforcement cage is simple to mount, convenient to dismount and high in repeated utilization rate.