Polyethylene terephthalate(PET) with high molecular weight is hard to be obtained due to the backward reaction of the global equilibrium reaction. As the reaction proceeds especially for the final stage of PET synthesis, the tremendous increase in viscosity prevents removal of the byproduct so that it is difficult to reach the high degree of polymerization. Many reactors have been developed to resolve this problem and are presently used in industry, but it is still interesting to see the other types of reactor to enhance the efficiency of the process. In this study to enhance the efficiency of polymerization, Rotating Drum Reactor was developed and its efficiency was tested. Bis-2-hydroxy ethyl terephthalate(BHET) monomer was fed into the reactor, where temperature was kept 280℃. Then volatile byproduct (EG) is continuously removed from the reaction mixture by controlling the pressure. Catalyst used was Sb₂O₃ and stabilizer was not used. Good result is obtained with proper surface renewal action by rotating the outer cylinder which was found to be the most important factor to remove the volatile byproduct. As espected reactor efficiency increases with decreasing the surface renewal time. The effect of vacuum pressure on the reactor efficiency was also tested.