It is difficult to lower the temperature of LNG storage tank in the later stage of pre-cooling when a new LNG terminal carries out the pre-cooling for the first storage tank through the first ship.The reasons for the above phenomenon are found out through theoretical analysis and HYSYS simulation calculation, which show that the shortage of available LNG due to temperature rise of unloading pipeline is the main reason for the difficulty in temperature drop of storage tank in the later stage of pre-cooling.Based on the experience in pre-cooling of several domestic LNG storage tanks, the recommended solutions to the above issues are proposed from the perspectives of design optimization and commissioning.In terms of design optimization, a certain amount of allowance should be properly considered on the basis of the theoretical maximum amount of pre-cooling of storage tank when designing and selecting pre-cooling pipelines, pre-cooling regulating valves and pre-cooling nozzles, while taking into account the flow loss of LNG caused by the above reason.In terms of commissioning, the by-pass valve of overhead charging valve can be opened slowly and regularly to increase LNG flow, so as to keep the temperature drop rate of LNG storage tank between the optimum range of 3～5℃/h in the later stage of pre-cooling.The research results can provide reference for the design and pre-cooling of LNG storage tanks of the same nature.