NOVELTY - Cryogenic fractionation of a gas mixture (raw gas) comprises cooling and partially condensing the gas to obtain a first gas/liquid mixture; discharging the sump product from the absorbing column and introducing into a rectifying column; discharging main gas from the rectifying column to obtain a second gas/liquid mixture; separating the second gas/liquid mixture; discharging the C2 rich liquid phase and splitting into a first and second C2 rich partial stream; leading the first and second C2 rich partial stream into the head of the absorbing- and rectifying column, respectively.    USE - The invention deals with the cryogenic fractionation of a gas mixture (raw gas) containing hydrogen and methane-poor C3 hydrocarbon into a C2 and C3 stream.    ADVANTAGE - The process of the fractionation of a gas mixture (raw gas) containing hydrogen and methane-poor C3 hydrocarbon into a C2 and C3 stream is economical.    DETAILED DESCRIPTION - Cryogenic fractionation of a gas mixture (raw gas) containing hydrogen and methane-poor C3 hydrocarbon into a C2 and C3 stream comprises cooling and partially condensing the raw gas to obtain a first gas/liquid mixture; introducing the mixture into an absorbing column; discharging the sump product from the absorbing column and introducing into the middle section of a rectifying column operated at least at the same or high pressure, where the pressure loss and pressure difference between the two column can be over come by a pump; discharging the sump product containing C3 hydrocarbons from the rectifying column; discharging main gas from the rectifying column with subsequent cooling to obtain a second gas/liquid mixture by partial condensation; separating the second gas/liquid mixture in a phase separator into a C2 rich liquid phase and a gas phase containing C2 hydrocarbons; discharging C2 rich liquid phase from the phase separator and splitting into a first and second C2 rich partial stream; leading the first C2 rich partial stream as recycled to the head of the absorbing column; and leading the second C2 rich partial stream as recycled to the head of the rectifying column, whose pressure is increased to a high value by a pump.