The invention belongs to the technical field of engineering plastics and discloses a polycarbonate composition and a preparation method thereof. The polycarbonate composition is prepared from, by weight, 10-94 parts of first polycarbonate, 1-50 parts of second polycarbonate, 5-30 parts of a acrylate polymer and 0.01-1 part of an interface regulator, wherein the first polycarbonate refers to straight-chain polycarbonate, and the second polycarbonate refers to branch-chain polycarbonate; a difference value of refractive indexes of the acrylate polymer and the first polycarbonate as well as the first polycarbonate is not greater than 0.08; the interface regulator refers to a GMA polymer. By combination of the straight-chain polycarbonate and the branch-chain polycarbonate, optimal selection of refractive index alloy and adding of the interface regulator, a uniform fine alloy phase state structure is formed, and the composition integrates high surface hardness, excellent impact performanceand great transparency, is comparable to PMMA in surface performance and achieves rigidity-flexibility balance of PC.