To investigate the effect of silica fume and limestone powder on the crack resistance for roller compacted concrete(RCC)and its mechanism, silica fume was added into the limestone powder-fly ash-based RCC. Indicators such as the split tensile strength, tension-compression ratio and elastic modulus-compression ratio were used for the experimental analysis with the technology of scanning electron microscopy(SEM), thermal gravimetric analysis(TGA)and mercury injection(Hg). It is suggested that adding 5% silica fume into the limestone powder-fly ash-based RCC of 40% admixture can increase the density of the microstructures, optimize the pore structures and effectively improve the overall crack resistance performance of the material.