A systematical analysis of the macro/microstructure, composition, and crystal orientation of the bright band were conducted using OM, SEM and EBSD methods, as well as Gleeble tests, to study the formation mechanism of bright band in forged TC18 alloy. The results show that: the bright bands in the center of TC18 alloy forgings correspond to β cube-grains in size of around 100mm; During the forging process, an inhomogeneous distribution of temperature and equivalent strain in the forging stocks is caused by adiabatic heating, which is an important reason for the microstructural heterogeneity; The large β cube-grains are formed due to the repeated compression along the orthogonal direction, which results in continuous strengthening of the <100> texture in the center of the forging stocks, and the merging of <100> grains with similar orientations; Through annealing treatment and compression along diagonal direction, it is possible to effectively reduce and avoid bright band defects in TC18 alloy.