The WSTi6421 titanium alloy billet examined in this study, following β annealing, displayed abnormally coarse grains (ACGs) that exceeded the size of adjacent grains, resulting in a non-uniform abnormal grain structure (AGS). Through electron backscatter diffraction (EBSD), the as-forged microstructure at various locations on the WSTi6421 titanium alloy billet was analyzed, showing that the strength of the β phase cubic texture developed during forging significantly influences the grain size post-β annealing. To delve into this phenomenon, researchers carried out heat treatment experiments to monitor the microstructural changes of the forging throughout the β annealing process. The temperature was incrementally increased from Tβ-50℃ to Tβ+10℃ during these experiments. Macrostructure observations and Scanning Electron Microscope (SEM) analysis demonstrated that the cubic texture of the β phase created by forging impacted the texture of the secondary alpha phase, which subsequently influenced the β phase formation during the post-β annealing process. Moreover, the pinning effect of the residual primary α phase plays a crucial role in the growth of β grains during the β annealing process. EBSD analysis findings suggest that the strength of the β phase cubic texture established during forging impacts the orientation distribution differences of β grains post-β annealing. Additionally, the development of large orientation grains within the cubic texture during β annealing shows a degree of selectivity, affected by various factors including the pinning effect of the primary α phase, the strength of the matrix cubic texture, and the orientation relationship between β grains and the matrix. In essence, the stronger the texture in a region, the less likely it is for large misoriented grains to undergo secondary growth, thereby intensifying the disparities in microstructure and grain orientation distribution across different regions after β annealing.