The invention discloses a manufacturing method of a polyester film. The polyester film has a high degree of crystallinity through adjustment on specific technology parameters of the transverse drawing technology, and therefore the polyester film has good heat resistance and size stability, and the flatness of products in the later heated machining procedure is improved. Meanwhile, in the production process, the number of pollutants in the polyester film is greatly reduced by improving the filtering precision of melt and controlling the cleanliness of a production workshop, the cleanliness degree inside and outside the polyester film is guaranteed, and accordingly the manufactured polyester film meets the requirement for the polyester film in the manufacturing process of a high-precision radio frequency identification tag antenna.