As for the simultaneous detection of trace Cu 2+ and Co 2+ in zinc solution, there exist the problems of low sensitivity, narrow effective band and serious spectral signal coverage. Thus, a multi-objective optimization fractional differentiation pretreatment method is proposed. First, the coverage degree and distortion degree in the simultaneous detection of Cu 2+ and Co 2+ are determined according to the spectral characteristics, and the functional relationship and constraints of differential order and index are fitted. Then, the established optimization problem is solved by the multi-objective particle swarm optimization algorithm. This multi-objective differential order optimization method is finally verified. The results show that the proposed method can be used to reconstruct the completely covered ion wave peaks with low sensitivity and narrow effective bands, and to solve the complete spectral coverage problem. Moreover, it can be used to minimize the distortion degree of differential filtering and reduce the spectral coverage of trace Cu 2+ and Co 2+ to the maximum extent.