Abstract: A preliminary study of the color reactions of Fe(Ⅲ),Ni(Ⅱ),V(Ⅴ),Cu(Ⅱ) and Co(Ⅱ) individually with 5-Br-PADAP in the the presence of OP and in an acetate buffer solution of pH 3.5,serious over-lapping of absorption spectra of these metal ion chelates was observed,leading to serious inter ferences among each other in their spectrophotometric determinations. By applying the algorithm of fuzzy-cluster-partial least square,the problems of spectra over-lapping and of optimization of calibration model for calculation in photometry were solved effectively. Under the optimized reaction conditions and by the use of the fuzzy-cluster-PLS algorithm,the 5 elements mentioned above were determined simultaneously. Test for recovery with 5 simulated samples gave results of recovery in the range of 93.3%-105.5%. In its application to the analysis of crude oil sample,the results obtained were in consistency with those obtained by AAS method.