Abstract: A system for removing slag from a boiler includes a laser, a targeting system, and a computer system for controlling the operation of the laser and targeting system. Preferably, the laser includes chemicals contained in a mixing pre-chamber. A pump connects to the pre-chamber, and an iodine laser diode connects to the pump. The laser unit also has a power source, cooling system, and a raw beam laser. The targeting system is driven by targeting software and includes an optical targeting system. Preferably, the system also includes a mobile trailer with a computer control room, a main laser operating unit, and a portable optical targeting system connected to the laser unit. Fiber optic cable connects the targeting system and the laser. The online deslagging method includes transporting and setting-up the system, relaying set-up information, feeding targeting information, activating and operating the laser to remove slag from within the boiler.