For the development of C36 Dimer fatty acid （DFA） as a modifier or raw materials to make a new type of modified unsaturated polyester materials, DFA-EG polyester was synthesized by direct melt polycondensation method, with C36 dimer fatty acid （DFA） and ethylene glycol （EG） as raw materials, p-toluene sulfonic acid （TSOH） as catalyst. The resultant polyester structure was characterized by fourier transform infrared spectrum（FT-IR） and nuclear magnetic resonance （^1H-NMR）, the thermal performance was characterized by differential scanning calorimetry （DSC） and thermogravimetric analysis （TGA）, and the relative molecular mass and its distribution of DFA-EG polyester were characterized by gel permeation chromatography （GPC）. The results showed that when n （ DFA ） ： n （EG） ： n （ TSOH ） = 1 ： 1.4： 0. 016, reaction temperature 165 ℃ and reaction time 6 h, the esterifieation rate of polyester 99. 30% could be obtained. The weight-average molecular mass was 8 643 g/mol, relative molecular mass distribution was 1. 227 8. The initial thermal decomposition temperature and glass transition temperature of 380 ℃ and - 13.3 ℃ respectively. Therefore, the DFA-EG polyester can be used as a kind of green environmental protection block polyester base material.