Abstract: Benzilic acid was found to be a specific masking agent for Ti(Ⅳ) at pH4.5-7.0. This paper reports that using the "DCTA-benzilic acid masking method", 3-100μg of Ti (in 35ml) can be accurately spectrophotometrically titrated at pH5.5 using standard zinc solution as the back titrant and xylenol orange as the indicator. The selectivity is very high. The following ions will not interfere. Th, Zr, Fe(Ⅲ), Al, Ga, In, Tl, Cr(Ⅲ), As(Ⅲ), U(Ⅵ), Mo(Ⅵ), Sc, Y, Yb, Nd, Cu, Pb, Ni, Co,Cd, Ag and the alkali earths. The TiO₂ content in quartz as little,as 0.005% can be accurately determined with this method.