the invention discloses a plant moisturizing composition which is prepared from the following raw materials in percentage by weight: 25.0-35.0% of a fragrant citrus extract, 15-20% of an algae extract, 10-14% of a chamomilla recutita flower extract, 5-9% of a gynostemma pentaphylla leaf extract, 3-7% of an abelmoschus esclentus fruit extract, 0.01-0.1% of a polyglutamic acid, and the balance of deionized water. A preparation method of the plant moisturizing composition comprises the following steps: A, taking the deionized water by weight percentage, and heating the deionized water to 45-55 DEG C; B, continuing to add the fragrant citrus extract, the algae extract, the chamomilla recutita flower extract, the gynostemma pentaphylla leaf extract, the abelmoschus esclentus fruit extract and the polyglutamic acid in a weight ratio; and continuing to stir for 10-20 min at a temperature of 45-55 DEG C and a rotating speed of 40 r/min until the materials are uniformly mixed; and C, reducing the temperature to room temperature, so that a finished product of the plant moisturizing composition is obtained.