The invention discloses a process for preparing a dendrobium officinale freeze-dried powder. The process comprises the following steps: (1) preparing a raw material, namely, washing dendrobium officinale which meets standards with water, removing impurities, and bleaching with purified water; (2) dicing, namely, cutting the dendrobium officinale into segments of 2-4cm by using a machine; (3) crushing and pulping, namely, crushing and pulping by using pure water in a solid-liquid ratio of 1g:(80-120)ml, screening by using a net of 28-32 meshes, and collecting filtrate; (4) performing vacuum drying, namely, performing pre-freezing on the pulp at minus 18 DEG C to minus 20 DEG C over night, performing vacuum freeze-drying for 16-22 hours, and finally sublimating for 12-18 hours; (5) crushing, tidily crushing the freeze-dried powder obtained in the step (4), and screening granules by using a net of 70-90 meshes, thereby obtaining the dendrobium officinale freeze-dried powder. Compared with the prior art, the process disclosed by the invention is simple to operate, scientific and reasonable in step, free of solvent pollution or residue in the preparation process of the dendrobium officinale freeze-dried powder, low in preparation temperature, and capable of ensuring that bioactivity of functional substances of the dendrobium officinale is not lost.