Rainbow colour mirror plating process is to use electrolysis to attach a metal film on the surface of stainless steel ball. The ball is first pre-treated with surface cleaning, adjustment and other pre-treatments, and then plating operation is carried out by selecting the appropriate plating solution formula and parameters. Its colour formation originates from the different thickness of the plating layer, so that the light reflection, interference, etc., coupled with the mirror polishing treatment, and ultimately presents a unique rainbow-coloured mirror visual effect.