The mitigation effect of waste rubber powder（WRP）， silica fume（SF） and their binary blends on alkali-silica reaction（ASR） was studied by accelerated mortar-bar test， and the effect of WRP sizes on ASR was compared. The inhibition mechanism on ASR was revealed by means of scanning electron microscope（SEM） and X-ray diffractometer（XRD）. The results show that WRP can inhibit ASR， where the particle size of WRP is a significant parameter. The mitigation effect of the 0.125 mm（120 mesh） WRP is the best . Though the inhibition effect of SF on ASR expansion is good at early stage， it turns worse in late stage. It is found to have an excellent synergistic effect on inhibiting ASR when it is mixed with SF and WRP. The pozzolanic reaction of SF at early stage generates gel with strong alkali absorption capacity， which improves the compactness of microstructure of WRP and mitigates the negative effects of ASR. In the later stage， WRP can effectively reduce the expansion pressure， so they can alleviate the expansion caused by ASR synergistically.