The invention discloses a preparation method of transparent bagged pure milk. The preparation method comprises the following steps: step 1: preheating raw milk, and then, performing cream separation treatment to obtain skimmed milk and cream powder; step 2: sequentially performing micro-filtration membrane sterilization and ultra-filtration concentration treatment on the skimmed milk; step 3: respectively performing high-temperature sterilization treatment on the skimmed milk obtained in the step 2 and the cream powder obtained in the step 1; and step 4: performing homogenizing operation on the skimmed milk and cream powder obtained in the step 3 in a certain proportion under aseptic conditions so as to obtain pure milk with different fat concentration. The transparent bagged pure milk prepared by adopting the preparation method disclosed by the invention has the advantages that the taste is smooth, the nutritional value is high, the stability of flavor and quality in a shelf life canbe kept, the preparation process is easy to control, and the pure milk of different batches has high stability.