Based on the problems in an offshore LPG production system, the HYSYS software simulation shows that high content of free water in the inflow to LPG production columns causes LPG recovery ratio lowering, product disqualification, operation fluctuation and potential flooding. The free water also causes foaming, heat exchanger scaling and equipment corrosion. The solution is to modify the traditional separator to serial high efficiency coalescence separator to remove the free water and emulsified water at the inlet of LPG system by stages and steps, so as to ensure the safe and stable operation and design life of the offshore LPG production system. The modularized design needs less space, weight and workload, which is of great advantages to the offshore production facilities.