The invention discloses a manufacturing method of powder materials for additive manufacturing. The method is characterized in that a minus 1000-mesh powder material is separated from ordinary water atomized iron powder, and the minus 1000-mesh powder material is conveyed into an atomizer through a high pressure air current and is adopted as core particles of a high-pressure cooling water medium toimprove fine powder rate and sphericility of powder material products. According to the method, minus 1000-mesh iron powder is adopted as a nucleation center and is dispersed in high-pressure high-speed atomized water, collision strength is improved, reaction free energy is changed when iron powder collides with molten iron or molten steel, solidification time is shortened while atomization efficiency is improved, and iron powder or steel powder with high sphericility and uniform particle size distribution is obtained; the adopted minus 1000-mesh iron powder is a low-value product in the normal production process and can be obtained through normal separation, the yield of a core product is increased while the utilization rate of the low-value product is increased, increase of impurity elements is avoided, and follow-up special treatment is not required; and the method is low in cost when utilized to manufacture iron powder or steel powder, and manufacturing cost of additive manufacturing products is greatly reduced.