Chloride ion ingression into concrete under flexural load is investigated in the paper. Concrete specimens have been stored in 3.5%NaCl solution or 3.5%NaCl + 5%Na2SO4 solution for 210 days. The effect of flexural load and sulfate ion to chloride ion transmission is studied. The experimental results show that sulfate ion reduces chloride ion transmission in concrete. But when concrete under flexural load, Sulfate ion has plus and minus effect on chloride ion ingression into concrete. When the flexural load rate is low, sulfate ion reduces chloride ion transmission. But the flexural load is high, the negative effect of sulfate corrosion plays a main role. When concrete exposed to 3.5%NaCl+5%Na2SO4 solution, chloride ion diffusion coefficient of concrete in tensile zone increases with flexural load. And in compressive zone, the chloride diffusion coefficient decreases first and then raises with increasing flexural load.