In the liquefied natural gas (LNG) terminal, during the compression process of boil-off gas (BOG), dropping liquid or heavy components condense on the filter screen of the BOG low-pressure compressor inlet, resulting in increased pressure differential and even compressor tripping. The poor load matching between the low-pressure and high-pressure compressors in series operation can easily lead to frequent compressor trips. To address the above issues, taking a certain LNG terminal as an example, a method combining theoretical and simulated calculations with field operation experience was employed to optimize the design of the low-pressure compressor suction knock-out drum and the series operation process of the low-pressure and high-pressure compressors from the process design aspect. The process optimization of the suction knock-out drum design improve the separation efficiency of liquid droplets or heavy components carried in the BOG, avoiding high-pressure differential alarms or compressor tripping caused by the accumulation of liquid droplets or heavy components on the filter element. The addition of a BOG buffer drum between the series-connected low-pressure and high-pressure compressors, with a certain buffering time, effectively balances gas load fluctuations, reduces the difficulty of operating the two compressors in series, and decreases frequent tripping caused by load mismatch. After optimization, the BOG treatment system of this LNG terminal has been running smoothly for a long time.