Hydraulic expansion type reamer while drilling

The invention discloses a hydraulic expansion type reamer while drilling. The hydraulic expansion type reamer while drilling comprises a body 1 and reamer blades 12, wherein three to five elongated slots in uniform distribution are formed in the middle of the body axially, strip-shaped oblique slide grooves 10 are formed in the lateral edges of the elongated slots, and the reamer blades 12 are embedded into the elongated slots of the body 1 and are in limiting slide fit with the oblique slide grooves 10 through own lateral face slide groove structures. A return mechanism is arranged at the position, above the reamer blades 12, of the body 1, and an expansion mechanism is arranged at the position, below the reamer blades 12, of the body 1. The hydraulic expansion type reamer while drilling, of the structure, has the advantages that the hydraulic expansion type reamer while drilling is simple in structure and convenient to operate, the reamer blades can be cleaned and cooled timely, and well drilling safety is improved since the body bears torque.