This work numerically evaluates the mixing behavior of a binary mixture with the same physical properties but different temperatures in a three-dimensional bubbling fluidized bed based on the coupling of computational fluid dynamics and discrete element method. General mixing procedure and mixing index are adopted to investigate the macroscopic mixing behavior of the solid phase. Moreover, the effects of superficial velocity and the initial temperature configuration of particle groups on the temperature evolution of the system are discussed. The results show that three mixing mechanisms induced by the bubbles can be identified. The time required for a system to reach the temperature dynamic equilibrium is different from that required for the spatial mixing. With an increase in the superficial velocity, the mixing procedure is enhanced, and the temperature of each particle group distributes more uniformly. In addition, the effect of temperature configurations of different particle groups appears at the initial stage of solid mixing. This initial effect weakens slowly and even disappears with time evolution.