Polymerized oil with high viscosity were synthesized by polymerization of soybean oil (SO) with catalyst of bentonite.Tung oil(TO) was added into SO and the effect of TO on the polymerization reaction was studied.The physical and chemical properties of vegetable oil based polymerization oil from SO and TO were studied.The results show that the optimal conditions of SO polymerization are that the mass fraction of bentonite catalyst and LiCl cocatalyst is 6% and 0.6%,respectively,the reaction temperature and time is 305 ℃and 6 h.The conjugated triene acid contained in the fatty acid of TO can promote the polymerization of STO and shortens the time that the polymerized oil reaches the desired viscosity.Compared with the mineral oils with the same viscosity grade,STO polymerization oil has better viscosity index and low temperature flow performance,higher carrying capacity and better antiwear performance,and a more superior frictionreducing performance at the load of less than 294 N.