Gives an overview of the general principle and method for optimum design of large capacity brown coal fired boiler combustion system in the light of the requirements for national key science technology projects, on the basis of brown coal fired boiler combustion system design theory, and with necessary considerations accorded the characteristics of Chinese brown coal, long previous experience with deisgn and operation of brown coal fired boilers, achievements in research on combustion of brown coal and brown coal fired boiler, and the design and operation of 300 MW boiler at shuangliao power plant as well.