The invention provides a method for controlling drum pressure of an exhaust-heat boiler, which comprises the following steps of: detecting smoke temperature of a flue which is connected with the exhaust-heat boiler; judging whether the smoke temperature of the flue changes or not; if the smoke temperature of the flue changes, regulating a steam pressure regulating valve to control the drum pressure of the exhaust-heat boiler. The method fully considers the impacts of various factors in the actual production to the drum pressure of the exhaust-heat boiler, regulates the steam pressure regulating valve in advance by judging whether the smoke temperature of the flue which is connected with the exhaust-heat boiler changes, thereby keeping the drum pressure of the exhaust-heat boiler stable.