The invention provides a method for manufacturing a large lustrous straight polyester filament yarn, in particular to a method for manufacturing the large lustrous straight polyester filament yarn which performs side-blowing cooling within a certain included angle. The method adopts the fusing direct-spinning means of a large lustrous polyester fused mass and comprises the following preparation technological processes: the large lustrous straight polyester filament yarn is obtained after preparation of the large lustrous polyester fused mass, preparation of a booster pump, preparation of a fused mass conveying pipe, preparation of a spinning box body, preparation of a metering pump, preparation of a spinning component, side-blowing cooling, oil application of an oil tanker, and extension in two directions and winding. The method is characterized in that: an included angle theta is arranged between the side-blowing direction and the major axis direction of a straight spinning micropore;a moderate cooling mode is adopted; the length of a windless area of a spinning nozzle of a spinneret plate is between 130 and 140 millimeters; and the shape of a cross section of the spinning micropore is dumb-bell geometrical shape formed by two symmetrical circular arcs on the end part and two internally contracted symmetrical arcs which are connected with the two circular arcs.