<正>In order to improve the tensile properties of poly（ethylene terephthalate）（PET）, we used the direct esterification method to synthesize PET in a home-made facility, and a certain amount of ethylene glycol （EG）, one of the two starting monomers, was substituted by glycerin （GE）. Four PETs with different GE contents were prepared to investigate the effect of GE on the crystallization and tensile properties of the prepared copolyester. The results showed largely improved tensile properties and increased crystallization temperature due to the possible erosslinking structure in PET by using a small amount of GE.