The invention relates to a method for preparing preservative-free mesembryanthemum crystallinum extract from lyophilized mesembryanthemum crystallinum powder. The method comprises steps as follows: H1, raw material selection; H2, equipment cleaning; H3, freeze drying; H4, superfine grinding; H5, irradiation sterilization H6, ultrasonic extraction; H7, centrifugal impurity removal; H8, micro-pore filtration sterilization. The method is characterized in that: the technology is simple, hydroponic mesembryanthemum crystallinum planted in a plant factory is selected as a raw material, so that highquality of the extract is guaranteed, effective active ingredients of the mesembryanthemum crystallinum are completely reserved with a low-temperature cryodesiccation based powder preparation technology and an ultrasonic enhanced extraction technology, the prepared mesembryanthemum crystallinum extract contains no preservatives, and furthermore, the mesembryanthemum crystallinum extract is rich innutritional ingredients such as mineral substances, amino acids, inositol, beta-carotene, vitamins and the like, has whitening, freckle-removing, moisturizing, anti-allergic repairing and anti-agingeffects and the like, and can be used for preparing high-end cosmetics with moisturizing, soothing, whitening, freckle-removing, anti-allergic repairing, compacting and anti-aging functions and the like, and considerable economic benefit is produced.