The invention relates to the processing technique of an aluminum alloy decorating part, in particular to the etching and spray painting composite technique of the aluminum alloy decorating part. The surface of the aluminum alloy decorating part is eroded after the etching technique and before the spray painting, the alkalinity of degreasing solution is regulated to have pH which is equal to 12 to 13 by adding 2-4g/L NaOH, uneven oxide scale layer at the aluminum surface is removed while removing the surface oil and waste. The products which are processed by using the method of the invention can weaken the appearance characteristic of cool metal color tone while maintaining the etching appearance metallicity and strong contrast degree, therefore, the aesthetic characteristic of the products is increased.