Random copolyesters were prepared from poly (ethylene terephtalate) (PET) oligomer and 1,3-propanediol (PG) by polycondensation procedure using varying amounts of PET oligomer and PG. Copolymer compositions have been identified by $^1$H-NMR spectroscopy. The compositions of the copolymers can be conveniently controlled by manipulation of the reaction conditions. Three hour polymerization at 26$0^{circ}C$ generated the copolymers with the highest intrinsic viscosity. Investigation of the thermal properties of the obtained polymers via DSC showed that the copolyester became completely amorphous when the composition of PG ranged from 30 to 65%. Sequence information of the produced copolyesters were obtained from $^{13}C$-NMR analysis. The ET-TP-ET and TT-TP-TT blocks could be distinguished from the unsymmetrical diester sequence ET-TP-TT. The sequence analysis indicates that all the studied copolymers have randomly distributed sequence structure.