TiCl₃ slurry is a vanadium removal reagent in the process of removing vanadium from crude titanium aluminum tetrachloride powder, among which AlCl₃ plays a catalytic role and is one of the key factors affecting the quality of vanadium removal reagent. TiCl₃ slurry is a kind of purplish red solution, which also contains Fe³⁺, Fe²⁺, V³⁺, V⁵⁺ and other colored metal ions. If AlCl₃ is measured by conventional complexometric titration or spectrophotometry, these non-ferrous metal ions will cause serious interference, and it is difficult to accurately judge the end point of titration. In the experiment, the co-existing ions such as Ti⁴⁺, V⁵⁺ and Fe³⁺ in the sample solution were removed by hydroxide precipitation method, and Al in the sample solution was determined by NH₄F displacement titration method. The effect of solution pH on separation results of coexisting ions was investigated. The experimental conditions including titration method, indicator and displacer were obtained. The interference tests of coexisting ions showed that the coexisting ions in solution had no influence on the determination when the relative error of measurement results was controlled within ±2.0%. The proposed method was applied for the determination of AlCl₃ in TiCl₃ slurry. The relative standard deviation (RSD, n=8) was less than 3.0%. The recoveries were between 96% and 102%. This method effectively solved the determination of Al in complex matrix. Meanwhile, it could also provide a reference for the composition analysis in other similar samples with complex matrix.