The invention relates to a preparation method of dendrobium officinale extractive used for cosmetics. According to the invention, the preparation method comprises the following steps: washing and smashing 60-70 parts by weight of dendrobium officinale, dispersing in water and mixing; adding 1.0-1.2 parts by weight of cellulase to a dendrobium officinale suspension liquid, agitating, and reacting for 2-5h; adding 0.7-1.0 part by weight of hemicellulase, agitating, and reacting for 2-3h; adding 0.6-1.2 parts by weight of pectinase, agitating, and reacting for 1-2h; readjusting temperature and adjusting pH value to 4-6, adding 0.6-1.2 parts by weight of mannase, then agitating, and sufficiently reacting for 2-3h; adding 1.0-1.5 parts by weight of neutral protease, agitating, sufficiently reacting, then filtering, and removing residue; and concentrating to 120-150 parts by weight to obtain the dendrobium officinale extractive. The preparation method is mild in process conditions, high in extraction rate, and wide in material source, the extractive is non-toxic and harmless to people, is good in moisturizing effect, and has wide development prospect.