Liquid Oxygen （LOX）/kerosene is currently the mainstream liquid rocket propellant combination because of its high thrust， high density specific impulse， and low cost. However， the propellant serial loading procedure is still widely used at present， with the shortcomings such as tediously long countdown timeline， and significant temperature rise of kerosene after loading. For engineering application of LOX/kerosene parallel loading， safety experimental demonstration was conducted iteratively through oxygen/kerosene sealing experiments， LOX/kerosene leakage experiments， and safety boundary experiments. The results show that the safety indicators of LOX/kerosene parallel loading are that the kerosene vapor concentration is less than 1.80%， which can be achieved by controlling the kerosene temperature to be less than 62.2 ℃ or the vapor temperature to be less than 41.8 ℃. Under the typical condition of leakage at the launch complex， even under extreme environmental conditions such as 40 ℃ temperature and airtightness， the maximum concentration of kerosene vapor is only 0.53%， hence LOX/kerosene parallel loading is still absolutely safe. The research results have been applied in the launch service of a medium LOX/kerosene launch vehicle since 2022， decreasing the propellant loading procedure by 64% and the countdown procedure by 33%.