Mixed fiber concrete has good durability.Aiming at the PVA and UPE mixed fiber concrete，we carry out the 120 d corrosion test by high concentration chloride solution，predict and analyze the bearing capacity and damage change law of reinforced concrete beams before and after chloride ion corrosion combined with the three-dimensional numerical simulation technology.The results show that the brittleness of non-fiber concrete and concrete with 0.2% fiber（0.1% PVA and 0.1% UPE）volume content increases after being eroded by sea water，peak stress and corresponding strain decrease.However，the addition of fiber can reduce the loss rate of the flexural bearing capacity and the strain loss rate corresponding to peak stress of the concrete beam subjected to chloride ion erosion，and increase the toughness of the beam.When the loading displacement is 20mm，the final tensile damage of the beam with fibers after seawater erosion is 4.9% less than the final tensile damage of the fiber-free beam.And the final compression damage of the beam with fibers is 16.2% less than the final compression damage of the fiber-free beam.