The influence of thermal-mechanical processing (TMP) parameters on the grain boundary character distribution evolution in a cold-rolled Ni-based superalloy was studied. During annealing treatment, growth accident model was considered to be the main mechanism for the formation of new Σ3 boundaries in the SRX grains. With the increasing annealing time and temperature, there was more time for grain boundary migration and the grain boundary migration was faster at the higher annealing temperature, which could stimulate the formation of Σ3 boundaries by increasing the frequency of growth accidents. In addition, the fraction of Σ3 boundaries decreased firstly with the increasing strain, and then increased again. At the strains of 0.1 and 0.7, the fractions of Σ3 boundaries reached around 60%, which was related to the well development of large grain-clusters. Besides that, the evolution of Σ1 boundaries, coherent Σ3 boundaries, incoherent Σ3 boundaries, Σ9 boundaries, Σ27 boundaries, and random boundaries were also analyzed in detail.