The invention discloses a moisturizing dendrobium stem extract and a preparation method and application thereof. The method comprises the following steps: (1) adding a solvent to dendrobium stem powder, stirring uniformly, sealing and standing for swelling to obtain a moisturized dendrobium stem medicinal material; (2) filling macroporous adsorption resin at the bottom of a percolation column of apercolation device, then filling the moisturized dendrobium stem medicinal material obtained in the step (1), adding a solvent for percolation extraction, and collecting a percolate to obtain the moisturizing dendrobium stem extract. According to the method, substances such as pigments, alkaloids and proteins can be simultaneously removed to reduce the risk of stimulation of the extract, and theactive ingredients of the medicinal material are not damaged. The process is simple and reasonable in design, convenient to operate, free of solvent residue and suitable for industrial large-scale production, and the obtained moisturizing dendrobium stem extract can be applied to the field of cosmetics.