The invention discloses a spraying gradual-change composite-plate mobile-phone back shell. The back shell includes a surface wear resistance ink layer, a PMMA film layer, a PC film layer, an LOGO pattern layer, a UV transfer-printing texture pattern layer, an optical film layer and a base color ink layer which are disposed from a top to a bottom in sequence. A first color ink layer and a second color ink layer laminated from a top to a bottom are also disposed between the LOGO pattern layer and the above UV transfer-printing texture pattern layer. Thickness of the first color ink layer descends from a left to a right in sequence. Thickness of the second color ink layer descends from a right to a left in sequence. Thickness of all parts of the gradual-change color ink layers in a length direction of the mobile-phone back shell is the same. Compared with the prior art, the mobile-phone back shell which can be made through research and development of numerous experiments and tens of yearsof work experience of the inventor shows a natural gradual-change effect, an outer surface of the entire mobile-phone back shell cannot have a color separation line, and is natural and beautiful, andthe technical problem that existing plastic back shells cannot be made with gradual-change texture is solved.