Two different grades of poly (ethylene terephthalate) PET waste materials were depolymerized by diethylene glycol (DEG) or monoethylene glycol (MEG) in presence of a novel catalytic system using zinc acetate with di methyl aniline (DMA) as a co-catalyst. The co-catalytic system's efficacy on the glycolysis reaction can be compared with currently used catalytic reaction which depends only on (zinc acetate). Then, the products obtained from glycolysis of two different PET wastes were reacted with maleic anhydride to prepare different unsaturated polyester resins. FT-IR, 1H-NMR, 13C NMR, GPC, DSC, and mechanical testing were used to characterize the properties of the reaction products in each step. It was found that the depolymerization of PET wastes in the presence of co-catalytic system proceeded faster compared with zinc acetate-catalyzed reaction. Moreover, in synthesis of unsaturated polyester resins. The curing behavior of these polyesters was studied after they were dissolved in styrene monomer. It was observed that the glycolyzed ingredients produced by the co-catalytic system with (MA) had a greater reaction rate than the glycolyzed product produced by zinc acetate. It was determined that (DMA) speeds up the synthesis of unsaturated polyester resins as well as have a major effect on the curing behavior of unsaturated polyester resin.