The invention discloses a preparation method of nylon powder for 3D (three-dimensional) printing. The preparation method comprises the following steps: adding a surfactant, a light absorber, a bulking agent, a viscosity reducer, an antioxidant and heat conducting power and the like into nylon powder, and stirring and mixing at a high speed to obtain modified nylon filler; adding the modified nylon filler, solvent oil and an emulsifier into a reaction kettle, stirring and heating to 180-260 DEG C to dissolve the nylon powder to a liquid, and stirring and emulsifying at a high speed to obtain a nylon high-temperature emulsion; quickly cooling the nylon high-temperature emulsion into a nylon suspension; and separating, washing, drying and sieving to obtain spherical nylon powder with diameters of 30-100 mu m. The preparation process disclosed by the invention is simple and feasible, the preparation time is short in period, and the process is easy to control and good in repeatability. The synthesized product is uniform in size distribution, regular in shape, spherical or size approximately spherical and good in heat conductivity of powder and mobility, so that the nylon powder has a wide application prospect in 3D printing materials.