A series of ash concretes with 5%, 10%, 15%, 20% and 25% rape straw was used to make the test samples with the water-binder ratio of 0.4, 0.45, and 0.5. The deformation, mass lost, and compressive strength of the samples were detected to evaluate the erosion resistance by the sulfate erosion test with complete soaking treatment. The results indicated that the ash concrete with water-binder ratio of 0.4 have the high resistance to sulfate erosion than that with water-binder ratio of 0.5. For the 15% rape straw doped ash concretes with water-binder ratio of 0.45, the resistance to sulfate erosion increased 46% than the normal concretes.