The invention relates to a preparation method of a lodging-resistant multi-difference polyester low elastic filament. The preparation method comprises the following steps: firstly, mixing nano sepiolite fibers, organic magnesium hydroxide whisker, organic barium sulfate nano powder, ethylene glycol, propylene glycol, p-hydroxybenzoic acid and sodium germanate to obtain a high-modulus composite alcohol solution; secondly, mixing organic wollastonite nano needle-like fibers, mica powder, polyethylene glycol, the propylene glycol, an antioxidant 1010, ethylene glycol antimony and protonated agent phosphoric acid to obtain a high-modulus composite promoter; thirdly, co-polycondensing the high-modulus composite multifunctional alcohol solution and the high-modulus composite promoter with purified terephthalic acid and the ethylene glycol to obtain high-modulus modified polyester; a melt of the high-modulus modified polyester is sprayed from a T-shaped spinneret orifice in a spinneret plate; the lodging-resistant multi-difference polyester low elastic filament is prepared by a special cooling mode and a low-temperature texturing process. The fiber prepared by the preparation method has multiple different properties of different crystallization, different orientation and different shrinkage; after different shrinkage, the appearance is good, and a brushed fabric prepared from the lodging-resistant multi-difference polyester low elastic filament is not easy to lodge.