The main objective is to research liquid food sterilization technology that uses high intensity pulse magnetic field (PMF) and to discuss the possible bio-effects of PMF on the microorganism cell. Taking sterilization of fresh watermelon juice as an example, the influence of magnetic field intensity and pulse number on bactericidal effect was studied. Results show that the overall bactericidal effect strengthens as magnetic field intensity and pulse number increase, and that bactericidal effect is best when magnetic field intensity is 2.53 T and pulse number is 20. When the pulse number reaches 40, the influence of magnetic field intensity on bactericidal effect strengthens at all times; when magnetic field intensity reaches 4.22 T, influence of pulse number on bactericidal effect strengthens at all times. However, under some parameters, the rebound phenomena of bactericidal effect appear, which requires in-depth discussion. The bio-effects of PMF on the microorganism cell, the mechanisms that destroy cell construction and those that hinder normal physioloical activity by PMF were analyzed from the viewpoint that PMF changes some of the parameters, such as cell span membrane potential, inductive electric current, Lorenz force of electrification particles and ion energy.