Disclosed is a smoke heater used for low-temperature smoke and a heating method of the smoke heater. Coal serves as the main fuel of a thermal power plant, and water and ash in the coal lead to the result that a large amount of water and dust are contained in the smoke generated after burning. If the smoke is discharged into the atmosphere at the low temperature, the water and the dust suspend and accumulate in the low-altitude atmosphere to form fog drops in a short time. The fog drops, dust and the rest pollutants are further combined, so that fog and haze pollution is very liable to be generated in the atmosphere. The smoke heater comprises a regulating valve (5) which is connected with a steam heater (3). The steam heater is connected with a circulating water pump (2) which is connected with a smoke heater body (1). The smoke heater body is connected with the steam heater which is connected with a water drain tank (4) through a pipeline.