With the increasing of human activities reflected by the economic developments, there are an enormous number of Municipal Solid Waste (MSW) which is the must to manage this waste in the proper way. Moreover, to response to Bio Circular Green Economy, using this waste as fuel for power generation in a state-of-the art waste incineration plant is one of the efficient ways for waste management including the reduction of greenhouse gas emission. In order to help the design of the sophisticated waste to energy plant, the combustion modelling to calculate mass and energy balance of the plant was developed as a design tool to determine the amount of combustion air, the amount and the composition of the exhaust gas from the combustion process, the steam production rate, and finally, the amount of electricity produced from MSW. The combustion modelling was developed on a spreadsheet and based on theory of combustion, mass and energy balance of sub-systems in a modern sophisticated waste incineration plant for energy production. The required input data are the amount, the moisture content, and the lower heating value, as well as the chemical composition of the waste, additionally, the criteria of pressure and the temperature of the steam produced are required. The combustion modelling has been run on a waste incineration plant with a treatment capacity of 500 ton per day with high moisture content and low heating value of the waste equipped with steam generator and turbine generator for power production. The results showed that the combustion temperature, the steam production rate and the amount of electricity produced depended on the moisture content and the lower heating value of MSW. By reducing the moisture content from 61.26 to 20 %-wt. and the lower heating value of waste increased from 1,655.11 to 3,417.95 kcal/kg and the combustion temperature increased from 582.30 to 1,206.75 °C. Steam production rate lied between 23.50 and 85.34 ton/hr and 3.55-12.88 MW electricity have been produced depending on moisture content of MSW and boiler efficiency. The results of simulation running by developed combustion modelling showed that the suitable moisture content of MSW needed to run the plant should not exceed 40 %-wt., since the combustion temperature of greater than 850 °C was achieved and 8.93 MW electricity was generated at boiler efficiency of 100 %. The developed combustion modelling can facilitate the design of a sophisticated waste incineration plant as well as to find out the optimum operating conditions of the plant.