The invention discloses an I-shaped high-strength reconstituted bamboo beam and a preparation method thereof. The I-shaped high-strength reconstituted bamboo beam structurally comprises a high-strength reconstituted bamboo upper flange, a high-strength reconstituted bamboo lower flange, a high-strength reconstituted bamboo web and low-density reconstituted bamboo shear-resisting bamboo pins, wherein the high-strength reconstituted bamboo upper flange and the high-strength reconstituted bamboo lower flange are connected with the upper portion and the lower portion of the high-strength reconstituted bamboo web through clamping slots A and B and the shear-resisting bamboo pins A and B. The I-shaped high-strength reconstituted bamboo beam and the preparation method thereof have the advantages that (1) on the basis of ensuring the bearing force of the beam, natural bamboo resources are utilized fully, and loads of building production to the environment can be relieved; (2) the flanges are formed by a sizing dimension, the height of the beam is adjusted through the height of the web according to the stress situation, standard production is facilitated, and the requirements for the assembly type structure and building variety can also be met; (3) the clamping slots and the shear-resisting bamboo pins are adopted for connection, the process is simple, connection is reliable, and quality is easy to control; and (4) the I-shaped section takes full advantage of the characteristics of high tension strength and high compression strength of high-strength reconstituted bamboo, the bearing efficiency of the beam is improved, materials are saved, weight of components is reduced, the preparation cost is lowered, and building assembly is facilitated.