Reactions between dislocations are investigated in two-dimensional colloidal crystals.It is found that,because of the conservation of total Burgers vectors,the kinetics of the reaction is dependent on the the symmetry of the crystal lattice.Merging is possible only when the total Burgers vector of the reacting dislocations is in line with existing crystal lines.In non-merging reactions,the number of dislocations cannot be reduced but the interacting dislocations can exchange their Burgers vectors and migrate to different gliding lines.The changing of gliding lines promises additional annihilation in multi-dislocation reactions.The bonding of non-merging dislocations determines the configuration and the orientation of the grain boundaries.The findings in this study may shed new light on understanding of dislocations and have potential applications in fabrication of crystalline materials.