The invention provides a solid oxide fuel cell generation system and a start up method thereof which heat up a reformer and a cell main body without any water and nitrogen gas, and start up for a short time until a power generation and without deteriorating a reliability of the cell. In a solid oxide fuel cell generation system having a power generation cell including an anode, a cathode and a solid electrolyte membrane, a mixing portion for obtaining a mixed gas by mixing a used fuel gas discharged from the anode with a raw fuel, a reducing combustion gas generating apparatus, and a reforming portion, the reducing combustion gas generating apparatus has a starting burner generating a reducing combustion gas, and the mixing portion, the reducing combustion gas generating apparatus, the reforming portion and the anode are coupled alphabetically from an upstream side.