Objective To improve the performance of triazene reagent, the synthesis of benzothiazolyl_2_aminoazo_4_methyphenyl (BTDAPMP) and its color reaction with titanium were studied in this paper. Methods BTDAPMP was applied to determination of trace titanium in human hair by spectrophotometry. Results In the presence of cetylpyridiniumbromid (CPB), Ti(Ⅳ) reacted with BTDAPMP to form a stable complex in a HAc_NaAc buffer solution at pH 5.5. The ratio of the amount of Ti(Ⅳ): BTDAPMP in the complex was found to 1∶2. The chromogenic reaction was completed within 5 min, and a steady color reaction was maintained for at least 4 h. In the color reaction, the apparent molar absorptivity was 1.21?10 5 L/(mol?cm) at 625 nm wavelength, Beers law was obeyed in the concentration range of 0～0.24 mg/L for Ti(Ⅳ). In the determination of trace Ti(Ⅳ) in human hair, the relative standard deviation (RSD) was less than 5% (n=7), the detection limit was 1.06?10-9 g/ml. Conclusion This method was highly sensitive and selective in determination of trace Ti(Ⅳ) in human hair.