The invention provides a process for recycling low-carbon hydrocarbon from carbon Fischer-Tropsch synthesis tail gas. The process can be used for obtaining a low-carbon hydrocarbon type mixture which mainly comprises C3-C5 by technological steps of raw material gas dehydration, cryogenic separation and the like. The process disclosed by the invention has the beneficial effects that a cryogenic process is a mixed refrigeration process which adopts a supercharged turbine expander for refrigeration and adopts a coolant for auxiliary refrigeration, so that the demand on externally supplied cold can be effectively reduced; meanwhile, during refrigeration, the power generated by turbine expansion of hydrocarbon-rich flashing steam acts on hydrogen-rich gas which is generated, so energy conservation is facilitated; a material flow which is at the lowest temperature can directly enter a cryogenic separation tower, so the operation temperature of the cryogenic separation tower is effectively reduced and the recycle rate of the low-carbon hydrocarbon is increased; heat of technological substances is exchanged directly, so that the investment in low-temperature heat exchanger equipment is lowered, the enterprise construction cost is lowered and relatively high economic efficiency is achieved.