<p>Corrosion will reduce the threshold for the expansion of existing cracks in steel structures. To establish the criterion for the propagation of existing cracks in corroded steel structures, it is necessary to study the microscopic mechanism of ductile fracture in the crack tip area of corroded steel plate. This paper aimed to investigate the void deformation characteristic in the crack tip region of corroded steel plates based on computational cubic cell models. By setting boundary constraint, the computational cell models considering the crack tip stress states with pit effects could be established. The pit did not change the evolution modes of the crack tip microscopic void, but the pit depth and shape had influence on the closing speed and degree of the micro-voids in the crack tip steel. The fracture initiation criterion of corroded cracked steel plates could be established based on the micro void evolution mechanism in the crack tip region considering pit effects.</p>