Preparation method and system of infant formula liquid milk

The invention discloses a preparation method of infant formula liquid milk, which comprises the following steps: preparing liquid milk which at least comprises raw milk, DHA (docosahexaenoic acid) and ARA (arachidonic acid); putting the liquid milk into ultrahigh-pressure equipment, and setting the pressure of the ultrahigh-pressure equipment to be a first pressure value; after a first time, obtaining a small amount of liquid milk from the liquid milk as a sample; obtaining the content of DHA and ARA in the sample; second time is calculated based on the ARA content in the sample and a preset ARA content minimum threshold value; and after a second time, setting the pressure of the ultrahigh pressure equipment to be a second pressure value, and maintaining for a third time to finally obtain the sterilized liquid milk, and cooling the sterilized liquid milk, and carrying out sterile filling so as to prepare the infant formula liquid milk. According to the invention, oxidation reaction of DHA and ARA is prevented