The invention relates to a burner structure of a rear-mounted steam heating furnace. The lower end part of a vertical ascending section hearth is connected with a horizontal burning section hearth, the upper end part of the vertical ascending section hearth is connected with a horizontal mixing section hearth, a gas burner is arranged outside the other end of the horizontal burning section hearth, a fume cooler is arranged in the vertical ascending section hearth, and a temperature measurer and an overheater pipe bundle are arranged in the horizontal mixing section hearth. By adopting the distribution manner of the rear-mounted burner, high-temperature fume generated by the gas through the combustion of the burner flows forwards along the hearth, then turns to ascend and turns to flush the overheater pipe bundle, a cooling device is arranged on an ascending area, and the high-temperature fume and a cooling gas are fully mixed in a mixing area for cooling, so that all parts of the overheater pipe bundle are evenly heated, a furnace pipe is prevented from being overheated and bursted; and the hearth adopts a C-shaped distribution manner, so that the residence time of a fuel in the hearth can be prolonged, and the sufficient burning of the fuel is facilitated.