Abstract: Thermoplastic polyester compositions, comprising: (a) 54-98% by weight of at least one polytrimethylene terephthalate; (b) 1-45% by weight of at least one impact modifier, and the at least one impact modifier is selected from ethylene copolymers having a general formula of E/X/Y, wherein: E is a radical derived from ethylene and accounts for 40-90% by weight of the total weight of the ethylene copolymer; X accounts for 9-55% by weight of the total weight of the ethylene copolymer and is a radical derived from a monomer having the following general formula: wherein, R1 is an alkyl containing 2-8 carbon atoms; R2 is H, CH3 or C2H5; Y is a radical derived from a monomer unit selected from glycidyl methacrylates and glycidyl acrylates and accounts for 0.5-40% by weight of the total weight of the ethylene copolymer; and (c) 0.01-3.0% by weight of a cationic catalyst, and the cation is selected from the group consisting of Mg2+, Sn2+, and Zn2+ and mixtures of these.