The invention relates to milk and a preparation method thereof, in particular to infant liquid milk supplemented with nucleotides suitable for 12 to 36 months babies, which belongs to the technical field of dairy products. The ingredients (in weight ratios) of the infant liquid milk are as follows: 400Kg to 600Kg of cow milk, 100Kg to 300Kg of skimmed milk, 1Kg to 5Kg of whey protein concentrate 34 (whey protein content of 33%), 2Kg to 10Kg of desalted whey powder D70 (whey protein content of 12%), 10Kg to 50Kg of vegetable fat powder, 5Kg to 15Kg of sucrose, 5Kg to 10Kg of dextrin, 100g to 500g of vitamin complex, 200g to 600g of complex minerals, 1Kg to 8Kg of stabilizers, 0.1Kg to 1Kg of nucleotides, and 300Kg to 500Kg of water.