The invention discloses a fresh-keeping liquid for fresh cut fruits and vegetables. The fresh-keeping liquid is prepared by compounding lactobacillus plantarum, carbon dots, ascorbic acid, citric acid, disodium ethylene diamine tetraacetate, glycerol and calcium propionate. According to the fresh-keeping liquid, the lactobacillus plantarum and the carbon dots are combined for fresh keeping of the fresh cut fruits and vegetables for the first time, the capability of lactic acid bacteria to inhibit the growth of spoilage bacteria and pathogenic bacteria is fully exerted, abundant radicals on the surfaces of the carbon dots are utilized, the water solubility, the reducibility and the antibacterial activity are good, the permeation effect on plant cells is enhanced, and the technical effects of synergistic bacteriostasis, sterilization and enzyme activity inhibition are achieved. All raw materials involved in a formula of the fresh-keeping liquid are of the food grade, the fresh cut fruits and vegetables can be directly eaten after being soaked in the fresh-keeping liquid, and the taste of the fresh cut fruits and vegetables cannot be adversely influenced. A preparation process is simple, the fresh-keeping effect is excellent, and the shelf life of the fresh cut fruits and vegetables can be prolonged to 12-15 days after the fruits and the vegetables are soaked in the fresh-keeping liquid and stored at the low temperature.