The utility model relates to a propane precooling heavy hydrocarbon recovery unit, its characterized in that: it includes a cold box, a precooling system and a heavy hydrocarbon piece -rate system, including many the pipelines that are used for the heat transfer in the cold box, the precooling system adopts tertiary the refrigeration to provide cold volume for handling the natural gas and LPG in the heavy hydrocarbon piece -rate system, and utilize high -pressure natural gas's self pressure energy, fully retrieve heavy hydrocarbon in the natural gas, improve the propane rate of recovery to reach better economic nature, heavy hydrocarbon piece -rate system internal plant is compact and simple. Behind the high temperature heating of first reboiler, from the liquid phase flow greatly reduced of first reboiler outflow to can reduce size, the volume of subsequent processing device, so that the installing and use of subsequent processing device, the utility model discloses can be applied to the operation of marine special environment, extensively be used for the high -pressure natural gas's of ocean production environment propane precooling heavy hydrocarbon to retrieve.