Abstract: Taking the 420t/h boiler of a power plant as example, the slagging mechanism was analyzed. Taking the slagging in furnace as judgment basis, the influences on the furnace temperature and slagging of different operation modes were introduced, including adjusting the air distribution mode，the amount of operation oxygen and reducing the load of the boiler.The best method to control the furnace slagging was proposed.

Key words: pulverized coal-fired boiler, slagging in furnace, experiment of combustion adjustment