Abstract: The sulphuric acid solution of titanium (Ⅳ) may form blue complex with 5-Br-PADAP in the absence of another organic acid. The sulphate anion not only influences the absorptivity of this complex but also alters the shape of the absorption spectrum of it; so it can be proved that the sulphate anion has entered the complex composition as a ligand, and the complex is a mixed ligand complex.In this paper,the conditions of the complex formation (include pH, concentration of various reagents, temperature etc.) are studied. The solvent effect of ethyl alcohol can improve the coloration reaction. The composition ratio in this complex is Ti (Ⅳ):5-Br-PADAPs SO₄^2-=1:1:2. By electrophoresis, the mixed ligand complex is proved to be in the form of anion with the formula of (TiO(HR) (SO₄)₂]^2- or (TiOR (SO₄)₂]^3- according to the pH of the medium. This conclusion is different from the commonly reported molecular formulas of mixed ligand complexes in similar ternary systems, such as those which have been reported by D.A.Johnson et al or C. B, Елинсон.