The invention provides a preparation method of a washing light blue leather material, and relates to preparation of leather materials. The preparation method comprises the following steps of 1, color alteration of a leather blank: enabling a full-automatic leather spraying machine to uniformly spray color alteration liquid onto the leather blank; 2, color alteration of a finished product: putting the treated leather blank in step 1 into an oil spraying table, utilizing a forming spraying technique to spray royalblue dyeing liquid onto the leather blank, and using a flatting agent and mixed wax to wash the leather blank until a double-color effect is realized; putting the washed leather blank with the double-color effect onto a polishing machine, and spraying a light matting additive A, wherein the rotation speed of the polishing machine is 19 revolutions per second; spraying a light matting additive B, wherein the rotation speed of the polishing machine is 9 revolutions per second; finally, spraying a light matting additive C, wherein the rotation speed of the polishing machine is 9 revolutions per second. The leather material prepared by the method has the advantages that the color is more saturated, the comfortability is better, an antiquing effect is realized, the color is particular, the color is more natural, and a color fixing effect is better.