The invention provides a carbon fiber reinforced Mg-base composite hollow pipe and a preparation method thereof. The preparation method comprises the following steps: preparing a core used for forming a center hole of the hollow pipe; weaving an integrally three-dimensional network perform from carbon fiber bundles by a weaving processing method; placing the perform in a metal mold to be preheated; pouring the smelted Mg alloy melt in the metal mold, and maintaining the pressure to prepare a pipe blank after forming under the extrusion pressure; and removing the core in the pipe blank to obtain the carbon fiber reinforced Mg-base composite hollow pipe. Three-dimensional carbon fibers are used as reinforcements, the center hole is prepared from the core with certain strength and easy to remove, and the problem of difficulty in preparation of a long tubular carbon fiber reinforced Mg-base composite is solved fundamentally.