The invention relates to a preparation method of polyester for an environment-friendly antimony-free film. The method comprises the following steps of (A) adopting terephthalic acid and ethylene glycol as basic raw materials to be made into slurry, adding the slurry into a reactor to have esterification reaction for 1h to 4h under the condition that the temperature is 220DEG C to 260DEG and the pressure is 0.1MPa to 0.3MPa, and obtaining an esterification product; (B) carrying out the pre-polycondensation reaction for 0.5h to 1.0h to obtain a pre-polymer under the condition that the reaction temperature is 240DEG C to 270DEG C and the pressure is gradually reduced from the absolute pressure of 101kPa to 600Pa; (C) carrying out the final polycondensation reaction for the prepolymer obtained in the step (B) for 1h to 2h to obtain a polyester product under the condition that the temperature is 270DEG C to 290DEG C and the absolute pressure is 150Pa to 50Pa. The liquid titanium catalyst and accessory ingredients of a given quantity can be added into the reaction system before or after the esterification reaction. The synthesized polyester does not contain precious metal such as antimony and is qualified in properties and suitable for producing a two-directional stretching film.