The invention provides a lactose-free infant formula food and a preparation method thereof. The preparation method disclosed by the invention comprises the following steps: adopting a dry-wet compounding process, namely producing vegetable fat powder by a wet process, and producing lactose-free whole milk powder by a lactose digestion process; performing dry mixing on the vegetable fat powder, thelactose-free whole milk powder, other main ingredients and auxiliary materials and bioactive substances, thereby obtaining the formula food suitable for lactose intolerant infants at an age of 0-12 months. According to the formula, the lactose is completely replaced with other carbohydrates, the lactose content of the product is less than 0.5wt%, and 1.8-2.2wt% of galactose having an important effect on brain development of the infants is remained. The protein in the formula is provided by lactoprotein, and the formula food is suitable to be eaten by the lactose intolerant infants so as to avoid lactose intolerance.