The invention provides a recovering system and a method of C2 in refinery dry gas by a compound adsorption method. The recovering system comprises a compressor, a pretreatment unit, a refinery dry gas cooling unit, a compound adsorption unit and a rectification unit. The adsorption unit comprises a gas-liquid separating tank, a C2 adsorption tower, and a methane desorption tower. The rectification unit comprises a C2 removing tower and an ethylene rectification tower. The refinery dry gas, after being compressed, pretreated and cooled, is subjected to gas-liquid separation to obtain a gas phase and a liquid phase. The gas phase is fed into the C2 adsorption tower and subjected to C2 adsorption by using a C4 mixture or a C5 mixture as an absorbent. The liquid phase is fed into the methane desorption tower, and subjected to methane desorption through stripping. The mixed adsorption oil at the bottom of the C2 adsorption tower and desorption gas at the top of the methane desorption tower are returned to the gas-liquid separation tank after being mixed and cold with the refinery dry gas. Tower bottom of the methane desorption tower is cooled and fed into the C2 removing tower and the ethane rectification tower to be rectified to obtain an ethylene product and an ethane product. The method provided by the invention adopts moderate operating conditions. The ethylene and the ethane both have the high recovering rate and the high purity.