Abstract: In order to investigate the influence of co-firing of multiple coals on the slagging characteristics at various positions in the furnace and to optimize the operation of the boiler, this paper establishes a 350MW front and rear wall opposed pulverized coal boiler model, which realizes the tracking of the particles and calculate the deposition rate of the particles on the wall. The results show that the overall slagging situation in the furnace meets the requirements of safe production when burning a single coal type. The main positions of slagging in the furnace under different furnace co-firing schemes are similar to the working conditions of a single coal type. While the two-coal co-firing scheme is adopted, the slagging situation in the furnace is better when the medium-volatile coal and the high-volatile coal are co-fired, and placing relative higher volatile coal at the bottom can effectively lighten the slagging at the bottom of the screen superheater. For the co-firing of three coal types in the furnace, if the proportion of high volatile coal entering the furnace is over 50%, the overall slagging situation is better. The injection position has a greater impact on the slagging of the side wall.