This power generation system consists of the gasifier, the steam boiler and the turbo generator set. The hot biogas generated is sent from the combustor into the steam boiler to supply heat without releasing any tar or sewage, where the exhaust gas is in compliance with the standard of environmental protection. The steam generated therefrom is sent to the turbo generator set for power generation and the heat supply network for centralized heating. This system is much more efficient for large scale power generation and environmental than the internal combustion engine.