With the rapid development of laser diode and the presence of advanced technology in thermal management and mode control, the average power of solid state laser has already rushed to 100 kW class in recent few years. The characteristics of solid state laser compared with chemical and gas lasers are outlined at first, followed by the detailed examination of several technical approaches which can enable 100 kW laser output, including heat capacity laser, thin disc laser, slab laser systems based on coherent combination, liquid cooling solid state laser(under HELLADS project) and finally fiber laser. After introducing the core concepts and presenting the current research status of these lasers, we conclude by pointing out the secrets behind the good beam quality.