Preset layering powder containing Ti+TiB2P, coarse TiB2P and fine TiB2P are taken to prepare TiB short fiber, with reinforcing Ti-based composite coatings on the surface of Ti6Al4V through laser synthesis in-situ. Volume fraction and length-diameter ratio of TiB short fiber are analyzed by scan electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the coating is mainly composed of TiB short fiber and TiB2P. When Ti+TiB2P acts as a preset layer, length-diameter ratio of TiB short fiber reduces as the content of Ti increases; when coarse TiB2P acts as a preset layer, the coating is difficult to form a large volume fraction of TiB short fibers; when fine TiB2P acts as a preset layer, high volume fraction and large length-diameter ratio of TiB short fiber can be formed in the coating. The formation mechanism is explained through microstructure evolvement rule of TiB short fiber in the coating.