A three-layer artificial neural networks was applied to simultaneous determination of zirconium and titanium by spectrophotometry. The conditons of simultaneous determination by color reaction of Zr(IV) ,Ti( IV ) with p-chlorophenyl fluorone in the presence of CTMAB were researched. The paralysis in the procedure of training was avoided with an improved error back propagation algorithms. This method was applied to the determination of synthetic samples and steel sample with satisfactory results.