Content of sulfate ions is relatively high in saline soil that can deteriorate the bearing capacities of bored pile and related studies are rarely reported. To clarify the evolution rules of bored piles' vertical bearing strength and the effects of pile length and pile radius on bearing strength after sulfate attack, bearing capacity evaluation model of bored pile was established based on the sulfate corrosive reactions and mechanism in sulfate corrosive condition. By combination with cases, the evolution rules of side resistance, end resistance and pile compressive strength were studied. The influences of pile diameter and pile length on bearing properties were analyzed and compared. The results show that the side resistance, the end resistance and the pile compressive strength change after sulfate corrosion. The side resistance of pile depends on stress redistribution and concrete deterioration around pile caused by sulfate corrosion products, and is also affected by the length and diameter of pile. The end resistance reduces with increasing depth of sulfate corrosion because the effective area decreases after corrosion. The compressive strength of pile decreases rapidly during sulfate corrosion process. It concludes that increase of pile diameter can enhance the resistance ability against deterioration, and the pile diameter increase can enhance the anti-sulfate corrosion ability for pile foundation design in saline area.