The invention discloses a refining process of trans-1,3-dichloropropene. Low-concentration trans-1,3-dichloropropene produced by a chloropropene apparatus is delivered into a rectifying column; an extracting agent in a feeding tank is fed to the top of the rectifying column via a feeding pump; the low-concentration trans-1,3-dichloropropene enters the rectifying column and mixes with the extracting agent; after rectifying and separation, overhead gas phase enters a condenser and is condensed via circulating water; a liquid phase enters a reflow tank; non-condensed gas phase enters a deep chiller; cold water is used to carry out secondary cooling before the liquid phase enters an impurity recovery tank; the non-condensed gas phase from the deep chiller enters a vacuum pump to ensure stablenegative pressure in the column; the liquid phase in the reflow tank is pressurized by a reflow pump, part of the liquid phase is delivered as a reflow liquid to the top of the rectifying column, andthe other prat of the liquid phase is used as finished high-concentration trans-1,3-dichloropropene. Through the continuous vacuum extraction process, the concentration of the trans-1,3-dichloropropene is increased to 99.5% and above, and the trans-1,3-dichloropropene is upgraded to medical-level application.