The invention discloses a workpiece inner hole surface polishing and strengthening integrated machining system and a method adopting additive manufacturing forming. The system comprises a workbench, an cavitation generation system, a liquid supply circulation system and a controller, the volume alternating mode is adopted to change the volume of liquid in an inner hole of the additive manufacturing forming workpiece to be changed by virtue of the rapid reciprocating motion of a piston, so that the pressure is changed, a hollow bubble group is formed at the inner part of the liquid and an innersurface of the inner hole, and the hollow bubble group is killed along with further compression, so that shock waves and high-speed water jet flows are generated in the liquid medium; a nano-colloidin the inner hole makes full contact with the inner surface of the hole, ultra-fine polishing of the inner surface of the hole is realized, the shock waves and the high-speed water jet flows on an inner wall of the hole, so that a certain amount of plastic deformation is generated on the inner wall of the inner hole, and the reinforcing of the inner surface of the inner hole is realized. The cavitation technology and the nano colloid polishing technology are organically combined, the fatigue life and the surface smoothness of the inner surface of the inner hole are remarkably prolonged, and the requirements on the ultra-smooth surface are reaches.