The invention discloses a preparation method of a six-leaf-section fiber. The preparation method is characterized in that molten polyethylene terephthalate is spun into fibers with six-leaf sections, and the fibers are mutually meshed. The preparation technology comprises the following steps: slice pre-crystallizing; slicing and drying; melt extrusion; melting and filtering; metering and pumping; spinning; cooling and blowing; bundling and oiling; mesh shaping; winding forming. The preparation method has the following benefits: the specific surface area of the fibers is increased, so that the coverage capability of the fibers is improved; leaves of the fibers are increased, and the fibers are meshed like gears, so that the cohesive force is increased; lots of gaps exist between filaments of the fibers, so that the fluffiness and the air permeability of a fabric are improved; the fibers are remarkable in antistatic property, moisture absorption and sweat discharging and good in hand feeling and warmth retention property; the surface of the fabric has a peculiar reflection effect; when the fibers are made into a fleece fabric, the villi can not only be mutually intertwined but also fluffy and erect, thereby being rich in stereoscopic sensation, fullness and solidity. The six-leaf-section fiber has the ladder prevention property superior to that of other fibers and is low in probability of pilling.