The invention discloses a cylinder type automobile rockshaft hole drilling mechanism which comprises a rack, wherein a holding fixing plate is fixedly arranged in the middle of the top surface of a top plate of the rack; clamping cylinders are fixed at both the front parts and the rear parts of two sides of the holding fixing plate; push blocks are fixed on push rods of the clamping cylinders; clamping blocks are fixed on opposite wall surfaces of two corresponding left and right push blocks; arc-shaped grooves are formed in the opposite wall surfaces of two opposite clamping blocks; a shaft to be processed is inserted into the arc-shaped grooves and is clamped among the four corresponding clamping blocks; side support plates are fixed at both the front part and the rear part of the left side of the top plate of the rack; two ends of a longitudinal screw rod are hinged with the two side support plates; a transverse moving motor is fixed on the outer side wall of one side support plate;an output shaft of the transverse moving motor is a splined shaft; and the splined shaft is inserted into a spline hole in one end of the longitudinal screw rod. By adopting the mechanism, a shaft tobe processed can be automatically clamped and fixed, holes can be drilled semi-automatically through manual operation, and the mechanism is good in effect and high in efficiency.