The invention relates to the technical field of metal materials, in particular to an Al2Y particle and carbon nano tube hybrid reinforced ultra-light magnesium-lithium-based composite material and a preparation method thereof. The magnesium-lithium-based composite material comprises the following components of, by weight, 5-20wt.% of micron-scale Al2Y particles, 1-5wt.% of nano-scale Al2Y particles, 0.5-3wt.% of a surface-nickel-plated carbon nano tube, 11-25wt.% of Li, and the balance Mg, and the total amount of impurity elements of Si, Fe, Cu and Ni is less than 0.02wt.%. The preparation method comprises the three steps of pre-treatment of the micron /nano-scale Al2Y particles, pre-treatment of the carbon nano tube and smelting. According to the composite material and the preparation method thereof, a beta-Li single-phase ultra-light magnesium lithium alloy is used as a matrix, and reinforcing phases with lower density are selected, so that the obtained magnesium-lithium-based composite material still has the excellent light-weight advantage; and the micron/nano-scale Al2Y particles and the carbon nano tube are used as reinforcing phases, so that different functions of the reinforcing phases of different types and scales in the reinforcement aspect are exerted, the cooperative reinforcement effect is achieved by utilizing hybrid reinforcement, the reinforcement effect is farhigher than that of a traditional reinforcing phase reinforced magnesium-lithium-based composite material of a single type and a single scale.