Since the spectra of Cu ²⁺, Co ²⁺, Ni ²⁺, Cr ³⁺ overlap seriously, it is not easy to determine single element and the principal component regression method for selective determination of Cu ²⁺, Co ²⁺, Ni ²⁺, Cr ³⁺ in their mixtures was developed and described. In the method, the transformation vector from abstract concentration matrix to true concentration was calculated with a set of standard samples and the principal component matrix. When having determined the transformation vector, it is used to predict the content of Cu²⁺, Co²⁺, Ni²⁺, Cr³⁺in unknown samples. The method here has been successfully applied to determine Cu²⁺, Co²⁺, Ni²⁺, Cr³⁺in the synthetic samples.