Abstract: Through three years' spot tracing of unstable operation of absorber and regeneration absorber of desulfurization system in LNG facilities, several control measures have been attempted. Through exclusive method and hydraulic study, it is shown that the flood caused by downcomer blocking of the acid gas absorber is the root reason that resulted in unstable operation of LNG facility in the northern China under high load. A comparison study on operation has been done after a complete change of the column vessels and internals. And the results have proved the judgment was right. Suggestions on both design and operation of amine unit of LNG plants have been presented.