NOVELTY - Recovering hydrogen, ethylene, and ethane from dry gas or separating ethylene cracked gas from dry gas of refinery plants comprises hydrating a dry gas or ethylene cracked gas; removing the hydrate produced mainly by methane and nitrogen from the gas phase; further separating the mixture comprising hydrogen, ethylene, and ethane obtained in the hydrating separation in a conventional freezing or absorbing separation; and decomposing the hydrate.    USE - For recovering hydrocarbon, ethylene, and ethane from dry gas or separating ethylene cracked gas from dry gas of refinery plants.    ADVANTAGE - The invention reduces operating difficulties and equipment investment and operating cost, can recover and concentrate hydrogen, and recovers 2C components that are high in economic value. It removes most of the methane from cracked gas before deep freezing to lower the cold load in deep freezing. It promotes the efficiency to extract the gases of high economic value from the dry gas or cracked ethylene gas of refinery plants and save energy for a further step.    DETAILED DESCRIPTION - Recovering hydrogen, ethylene, and ethane from dry gas or separating ethylene cracked gas from dry gas of refinery plants, where a hydrating separation is combined with a freezing or absorbing separation to separate a multiple gases mixture, involves providing a dry gas or ethylene cracked gas to be separated by hydrating separation into a hydrating reactor; removing the hydrate produced mainly by methane and nitrogen from the gas phase, thus obtaining the remaining mixture mainly comprising hydrogen, ethane, and ethylene in the gas phase; further separating the mixture comprising hydrogen, ethylene, and ethane obtained in the hydrating separation in a conventional freezing or absorbing separation to obtain hydrogen, ethylene and ethane as a product in two material streams for leaving the separation system; and providing the hydrate produced in the hydration reactor during the hydrating separation into a hydrate decomposer where the hydrate is decomposed under the conditions of heating or decompression to obtain gases mixture mainly comprising methane and nitrogen and less amount of ethane and ethylene.