Abstract: Through multi-wavelength spectrophotometry, the contents of four kinds of metal ions (Fe, Cu, Cr, Ni) can be determined simultaneously in this paper. The interferences of usually existing ions of Ca, Mg, Zn on measurement are discussed, and the best absorption wavelengths of the four metal ions are found out. The molar absorption coefficient under the specific wavelength is determined, and the complete linear equation is established. To verify the accuracy of the linear equations, the prepared mixed solution of Fe、Cu、Cr、Ni is measured by this method, and the result shows that the relative error can be controlled within ±5 % . Considering the content of metal ions can be varied in different realistic samples, the lower limit of this method was studied. The experimental result shows that the lower limit of Fe, Cu, Cr, Ni are 5 ×10^-4 mg/mL, 1×10^-3 mg/mL, 5×10^-3 mg/mL, 5×10^-3 mg/mL, respectively, and the reliable result of quantitative analysis can be obtained when the concentration of samples can exceed that. Finally, the content of Fe, Cu, Cr, Ni in electroplating sludge are measured, and the result is consistent with atomic absorption spectrophotometry.