The invention discloses a high-speed extrusion high-strength deforming magnesium alloy and a preparation method thereof. The provided magnesium alloy is subjected to high-speed extrusion under the condition of a high extrusion ratio, i.e. the extrusion speed can be more than 25 m/min under the conditions that the extrusion ratio is not less than 30 and the profile size is complicated, thus mainly solving the problem of greatly increased manufacturing cost due to low post-machining deformation rate of the high-strength magnesium alloy. The magnesium alloy finally obtained through extrusion has very high mechanical properties, and is applicable to blanks and the like for 3C (computer, communication, consumer electronics) product shells, leisure product bearing structures and aerospace components. The preparation process of the material is simple and low in cost, and has favorable industrialization prospects.