Abstract: Impact on slagging in furnace of different co-cumbustion methods with Shenhua coal and other coals were introduced.The experiment of switching burning for Shenhua coal and Yanzhou,Datong coal were carried out.The results show that slagging is aggravated during coal switching,the reason of which is analysised.Finaly,the reason of falling chips is explained with interrupted co-cumbustion method.