Tilting burners are widely used in p.f.-fired utility boilers. When burners are tilted, overall flow pattern in furnace are influenced. Fouling and slagging often occur in furnace waterwalls, convection superheaters and reheaters, and ash hoppers, which forces utility boilers shutdown. In order to ensure p. f- fired boilers operate smoothly and economically, to prevent slagging and fouling, series of tests have been conducted on a 600MW utility boiler and its 1/15 scale model. Results show, although tilting burners can realize steam temperature control, burners tilted downwards or upwards long-term in a large angle should be prohibited in operation.