The invention discloses a boiler main steam temperature control system. The boiler main steam temperature control system comprises a water supply system and a main steam system. The main steam system is provided with a boiler drum and further comprises a first-level overheater, a first-level temperature reducer, a platen superheater, a second-level speed reducer, a second-level overheater and a steam header, all of which are sequentially arranged on an output steam air path of the boiler drum. Through mutual influences and cooperation of a master controller, a first temperature reduction control module and a second temperature reduction control module, the main steam temperature is controlled, the main steam temperature is stabilized, and the accumulated error of the main steam temperature is reduced. The boiler main steam temperature control system has the beneficial effects that main steam temperature control is stable, the response speed of interference signals is high, influences on main steam from interference are reduced, and the main steam accumulated error is small.