To obtain better microstructures, a new aluminum grain refiner, Al-Ti-B-RE master alloy, was synthesized by the mix-molten method. Analyzed by thermodynamics and kinetics, the synthesis reactions of Al-Ti-B-RE master alloy would be possible, existent and to the right spontaneously. The second phase particles of the Al-Ti-B-RE master alloy mainly contained A13Ti, TiB2 and Ti2A120RE, etc. Under appropriate conditions, the second phase particles could be distributed homogeneously in the matrix. The morphology and the distribution of second phases of Al-Ti-B-RE master alloy, refining effects and mechanical properties were studied by XRD, SEM，OM and the electron all-purpose test machine (CSS-44100). The refinement experiment indicates that the self-made Al-5Ti-1B-1RE master alloy can refine the commercial pure aluminum into the level of the average grain size less than 150 μm, which belongs to the fine grain category. The tensile testing results show that after the addition of 0.2% self-made Al-5Ti-1B-1RE master alloy grain refiner into the commercial pure aluminum, the mechanical properties are improved significantly. Under the same condition, compared with the commercial pure aluminum without refinement, tensile strength σb and elongation δ are increased by 28.39 MPa and 29.97%, respectively. It is evident that the self-made Al-5Ti-1B-1RE master alloy grain refiner is superior to some domestic Al-5Ti-1B grain refiner