La 2 O 3 is added into boriding agent considered as a role of boriding catalyst to improve the growth of TiB crystal whiskers in commercial purity titanium (CP-Ti) substrate by electrolytic boronising technology. The catalytic mechanism of boriding catalyst is discussed. The boriding of CP-Ti substrates is carried out in an electrochemical cell in which we use a mixture of sodium tetraborate and potassium carbonate as the base ingredients of molten electrolyte. Both TiB 2 and TiB phases in the borided titanium samples are confirmed by X-ray diffraction method (XRD). Scanning electron microscopy (SEM) images reveal the boride layers consist of a homogeneous TiB 2 phase on the top and TiB whiskers toward the substrate, and the result verify boriding catalyst promotes the growth of crystal whiskers significantly with an average boride layer thickness of 132 μm and a maximum thickness 338 μm.