Copolyesters consisting of dimethyl terephthalate (DMT), ethylene glycol (EG) and poly(ethylene glycol) (PEG) were synthesized and their mechanical properties were evaluated along with shape memory function. In this investigation PEG with different mole ratio and molecular weight was used in order to prepare copolyesters. Experimental results showed that the strain at break, and notched Izod impact strength increased as the PEG content increased. Shape retention rate decreased slightly as the PEG is introduced, however, shape recovery rate increased as the PEG content increased. Overall shape retention rate decreased, whereas, shape recovery rate increased as the molecular weight of PEG increased. Thus, by adjusting the PEG molecular weight and mole ratio, it is possible to obtain copolyesters with excellent mechanical properties and good shape memory function.