The invention discloses a lactein drink for animals by using whey. 20-25 parts of whey of the secondary product in cheese processing are taken by weight and warmed to 43-45 DEG C; one part of production baking agent is taken for inoculating, stirring, packaging and capping; placing the materials at a room temperature or fermenting at a constant temperature of 30-37 DEG C, and overturning or oscillating every 12h, wherein finished products are realized in seven days at the room temperature and in 48h at a constant temperature of 30-37 DEG C. The drink contains a great amount of lactic acid and live lactic acid bacteria, improves the activity of pepsinum by more than three times, is beneficial to complete zymolysis of glycinn irritability antigen, solves nutritional and irritability diarrhea of weaned pigs, establishes mycelium balance of intestinal canal microbe of piglets, has rich milk smell and microbe metabolin and is beneficial to improving the feed intake and growth speed of piglets. The product has obvious effect applied to laying hens and is low in cost by using the whey of the secondary product in cheese processing.