Abstract: Recycled aggregate concrete can be regarded as a five-phase composite composed of newly hardened mortar, old hardened mortar, recycled aggregate, internal interface transition zone and external interface transition zone. The random aggregate program based on plastic damage constitutive relationship was generated by Matlab to determine the location information of random aggregate, and the finite element method was used to simulate and analyze the failure and crack growth of recycled aggregate concrete materials under different replacement rates. Considering the meso-structure characteristics, a two-dimensional recycled concrete model was constructed to study the mechanical properties of recycled aggregate concrete models with different replacement rates under uniaxial compression and tensile loads. The research results show that the recycled aggregate concrete specimens with a higher replacement rate will initiate crack formation earlier, and the cracks grow faster until they run through the whole slab; the elastic modulus of the new hardened cement mortar and the old hardened cement mortar thickness will also affect the formation of cracks.