As laser materials, bonding crystals have an efficient thermal management. They can decrease the deformation and fracture at the end face of crystals, and reduce wavefront distortion of laser. Based on the bonding interface gap closing theory, the bondability criterions of laser crystals are analyzed, the Hamaker constant and surface energy are calculated when Nd∶YAG, Nd∶YVO4 and sapphire are optical contacting, the bondability criterions for the three composite crystals are discussed, and the difficulty in crystal bonding is compared. Taking the YAG-Nd∶YAG crystal for example, the optical contacting experiment verifies the rationality of the bondability criterions, and the pump experiment for the bonding crystal after heat treatment proves that the bonding strength and the bonding stability fulfill the experimental requirements. The method for judging crystal bondability criterions provides references for selecting bonding materials and optimizing bonding process parameters.