Serious slagging occurred in burner region of a tangentially-fired supercritical 600 MW unit boiler.Numerical simulation was carried out for the combustion process with the Fluent software.The results show that the slagging position is close to the corners of the burner along the stream direction.Low oxygen content and high temperature(higher than the ash softening temperature(ST))are considered as the major reasons for slagging.When the surrounding air is increased to 60m/s

the temperature at the slagging position of the cross section is lower than ST.By this way the slagging problem can be solved and the safety and economy of the boiler operation can be improved.