The invention firstly provides a cast-in-situ dado structure for a manually excavated pile. The cast-in-situ dado structure comprises a locking beam on the horizontal plane of an orifice soil body and a dado on the pile side wall, and the dado comprises an orifice connecting section dado body and a hole interior section dado body. The invention further provides a construction method for the cast-in-situ dado structure for the manually excavated pile. A dado system for the manually excavated pile is formed in the mode that steel reinforcement cages are bound and concrete is poured in situ, and thus the problem that transportation and hoisting of prefabricated dados are difficult in mountain areas can be solved, the size of the dado system can be flexibly adjusted according to the size of the pile body, and the strength and stability of the dado are higher than those of prefabricated dados.