The utility model provides a propylene refining system comprising a propylene refining tower (20) comprising an inner cavity and a top access port (21) and a bottom access port (22) communicating with the inner cavity, a molecular sieve arranged in the inner cavity, and a collection tank (30) connected with the bottom access port (22). The system is characterized in that the system also comprises a heat exchanging assembly with one end connected with the collection tank (30) and the other end connected with the top access port (21). The heat exchanging assembly is used for heating liquid-phase propylene from the collection tank (30). The liquid-phase propylene is heated and forms gas-phase propylene; and the gas-phase propylene is refluxed to the propylene refining tower (20), such that the propylene absorbed on the molecular sieve is desorbed. With the technical scheme provided by the utility model, a problem of high propylene loss of a propylene refining process in prior arts is effectively solved.