The invention relates to a method for producing infant formula milk powder from desalted whey liquid. The method comprises the following steps: dissolving salt-containing whey powder with water at 35-50 DEG C to prepare salt-containing whey liquid with the dry matter content of 10%-20%; removing parts of positive ions by using positive ion exchange resin; lowering the pH to 1.8-3.0 to control the reproduction of microorganisms; carrying out multi-step desalting in sequence by nano-filtration, electro-osmosis and negative ion exchange resin to obtain desalted whey liquid with the dry content mass percent of 12%-30%; and standardizing the pH to 6.3-6.9 with one or two of mineral alkali liquor of sodium hydroxide or potassium hydroxide so as to obtain the desalted whey liquid suitable for producing the infant formula milk powder. According to the method, not only can deep desalting be carried out, but also microorganisms are effectively controlled in a desalting process, so that a phenomenon that microorganisms are controlled by a heating sterilizing manner after the desalting process is avoided. A process method of positive ion exchange, nano-filtration, electro-osmosis and negative ion exchange is selected and the salt-containing whey powder is processed into the desalted whey liquid with the ash content suitable for the infant formula milk powder; and the use amount of the desalted whey liquid in the formula milk powder is 350kg-3500kg per ton of powder.