The invention relates to the technical field of metal materials, in particular to an Al2Ca particle and carbon nano tube hybrid reinforced ultra-light magnesium-lithium-based composite material and apreparation method. The composite material comprises the following components of, by weight, 5-20wt.% of micron-scale Al2Ca particles, 1-5wt.% of submicron-scale Al2Ca particles, 0.5-3wt.% of a carbonnano tube with the surface plated with nickel, 11-25wt.% of Li and the balance Mg, and the total amount of impurity elements Si, Fe, Cu and Ni is less than 0.02wt.%. The preparation method comprisesthe three steps of pretreatment of the micron-scale / submicron-scale Al2Ca particles, pretreatment of the carbon nano tube and smelting. The beta-Li single-phase ultra-light magnesium-lithium alloy isused as a matrix, and the reinforced phase with relatively low density is selected, and then the obtained magnesium-lithium-based composite material still has the excellent light-weight advantage; themicron-scale / submicron-scale Al2Ca particles and the carbon nano tube are used as the reinforced phases, then different functions of the reinforced phases of different types and scales in the reinforcement aspect are played, the cooperative reinforcement effect is achieved through the hybrid enhancement, and the reinforcement effect is far higher than that of a traditional magnesium-lithium-basedcomposite material reinforced by the reinforced phase of the single type and the single scale.