We discuss the possibility of treating peri-implantitis by Er:YAG laser from a series of studies. Analyzing the possible physical, chemical changes and thermal effects and changes of biocompatibility of implants while treating implants by laser shows the promising application of Er:YAG laser. Recent clinical studies also showed that laser application could decrease inflammation around implants effectively. Treating peri-implantitis by laser may provide us a more effective and faster therapy than conventional therapy.