A polyester film and a method for producing the same are provided. The polyester film includes a heat resistant layer. The heat resistant layer includes a high temperature resistant resin material and a polyester resin material. The high temperature resistant resin material and the polyester resin material are melted and kneaded with each other via a twin screw granulator. The twin-screw granulator has a twin-screw temperature between 250° C. and 320° C., and the twin-screw granulator has a twin-screw rotation speed between 300 rpm and 800 rpm, so that the high temperature resistant resin material is dispersed in the polyester resin material with a particle size of between 50 nm and 200 nm.