The invention belongs to the heat treatment technology or the technical field of spheroidal graphite cast iron structural material machining. The low dual critical temperature is adopted for carryingout austenitizing and quenching and low temperature tempering. Particularly, the first critical temperature is the eutectoid transition point A1, heat preservation is carried out under the first critical temperature or the close temperature, and a spheroidal graphite cast iron matrix is in transition to the hypoeutectoid component from the eutectoid component; the second critical temperature is the austenitizing temperature A3 point of hypoeutectoid steel, heat preservation is carried out under the austenitizing temperature A3 point or the close temperature, the matrix is mainly characterizedas hypoeutectoid steel insufficiency austenitizing, after quenching, after quenching, at the interface from the edge of spheroidal graphite to dendrite, the gradient control structure with the dendrite as the unit is obtained, and is a little non-converted ferritic toughening subcritical quenching structure and comprises eutectoid steel and nearly eutectoid steel fine martensite and not completelydissolved carbide, low tempering reduces quenching stress, and the matrix is toughened; and the advantages of being high in process yield, excellent in wear resistance, capable of reducing energy consumption, friendly to the environment, simple, easy to operate and the like are achieved.