The invention relates to a gas 
dehydration and dealkylation method for a supersonic vortex tube, wherein the feed gas enters a separator and a filter separator to separate large particles out, the filtering separated feed gas and a 
dry gas are cooled in a first level gas-to-gas 
heat exchanger, and enter a first level prewhirling pre-
nucleation supersonic vortex tube to be dehydrated after fine and small 
solid particles are separated out through a fine filter, and are separated into a first level 
dry gas and a gas-liquid mixture; the gas-liquid mixture enters a first level gas-liquid separatorto be separated; the separated 
gas phase flows into the first level 
dry gas to enter a second level gas-to-gas 
heat exchanger; the cooled first level dry gas enters a second level prewhirling pre-
nucleation supersonic vortex tube to be dehydrated, and is separated into a second level dry gas and the gas-liquid mixture; the gas-liquid mixture enters a second level gas-liquid separator to be separated; the separated 
gas phase is interflowed with the second level dry gas to enter the second level gas-to-gas 
heat exchanger and the first level gas-to-gas heat exchanger for exchanging heat with thefirst level dry gas and the feed gas for temperature rise, and the heated dry gas is exported; and the high water 
dew point and blockage problems of 
hydrocarbon are solved, the 
dehydration and the dealkylation of the feed gas are realized, and a purification device is ensured to stably operate.