Abstract: Sample of petroleum products was burned and ignited to eliminate hydrocarbons,and the residue was dissolved in dil.HCl.A aliquot of the sample solution was taken for simultaneous spectrophotometric determination of Fe3+,Ni2+,V(Ⅴ) and Co2+ with 5-Br-PADAP as color reagent.Values of absorbance were taken in the range of wavelengths between 540-620 nm at 2 nm intervals,using reagent blank as reference.Data of absorption spectra were treated by wavelet-transform to filter the noise from the analytical signals.The analytical data were then analyzed by the algorithm of least square support vector machine (LSSVM).As shown by the results,the algorithm of LSSVM showed its special features of speedy calculation,high accuracy and good generalization.In pretesting of LSSVM with some simulated samples,values of recovery for the 4 elements were found in the range of 96.0%-103.5%.In analysis of substantial samples,results obtained by this method were in conformity with those obtained by AAS.Values of RSD′s (n=8) for all the 4 elements were less than 4%.