KR-215 is a universal nylon leveling agent with less foam; it can be used for ordinary acid dyeing; it has high affinity with fiber, and can improve the effect of different acid dye combinations with different affinities to fiber, especially recommended for lake blue color with high affinity to fiber; it has good retarding and transferring effect, and has no effect on the dyeing rate of dyestuff, and it can obtain very high final rate of obtaining color.