Propylene fractionator is the important fractionator for ethylene cracking plant and methanol-to-olefin/
propylene plants (MTO/MTP), is the final separation apparatu that separates propylene and propane to give polymer-grade propylene. A new pressure control method of the propylene fractionator was introduced, some problems existing in its use were described and  the principle and characteristics of thermal bypass control method were introduced, the advantages and disadvantages of the two kinds of pressure control method were compared. Although the new pressure control method can control the fractionator pressure, it has many shortcomings, so it should be chose carefully in the production.