The invention discloses a dyeing method for nylon-56 fibers. The dyeing method comprises the following steps that 1, dye liquor is prepared, wherein the dye liquor is prepared from acid dye, a leveling agent O and an acid-releasing agent shown in a formula I; 2, the nylon-56 fibers are immersed into the dye liquor, and dyeing is achieved at the temperature of 50 DEG C-90 DEG C. According to the dyeing method, the acid-releasing agent can be gradually decomposed into polyether and butanedioic acid at high temperature (higher than or equal to 50 DEG C), the pH value in a dyeing bath is controllably decreased by regulating the adopted polyether structure, therefore, the pH value of the nylon-56 fibers is gradually decreased to 3.5-4 from 6.5-7 in the initial dyeing stage, and the dyeing process is carried out smoothly and slowly.