The utility model relates to a refining system for circulating 1,3-propanediol in a continuous production process of polytrimethylene terephthalate (PTT), comprising a refining tower, a 1,3-propanediol collecting device connected with the refining tower, a refined PDO (Propanediol) cooler, a tower top steam condenser, a tower kettle liquid circulating pump and a vacuum pump, wherein the refining tower is a plate type or plate type/filling tower; the refining tower is provided with a mixed material inlet and a refined PDO outlet; the outlet of the 1,3-propanediol collecting device is connected with the mixed material inlet; and the tower kettle liquid circulating pump is arranged between a tower kettle liquid outlet of the refining tower and a material inlet of a re-boiler of the refining tower. According to the refining system provided by the utility model, the purity of the refined PDO is high and the water content is low, so that the quality requirement of a PDO raw material for manufacturing the PTT is met and the refined PDO can be circularly used for the continuous production of the PTT; and with the adoption of the refining system provided by the utility model, the refining can be continuously carried out, so that the refining system is applicable to the continuous production of the PTT.