In considering that differentligand complexes are sensitive and selective, we have studied the complexformation of uranium (VI) with 2,3,4-trihydroxy-3′-nitro-4′-sulphoazobenzole both in the presence and the absense of dyphenylquuanidine. The dependence of complexformation on pH of solution, time, concentration of reagent and third component studied. The spectrums of absorption obtained, the molar coefficients were calculated, compositions of complexes determined, using the techniques of izomolar series and techniques of Starik-Barbanel. The influence of foreign ions and masking agents were studied.