Calorie of the waste to be burnt has been increased comparing to the original design value at an existing MSW incineration plant. Incineration capacity and quality of the flue gas exhausted from the plant could be improved by adapting of Water-cooled stoker system with keeping the flue gas amount within the maximum original design value. By the improvement of the plant, total expenses of the waste treatment operation were reduced including of the initial modification cost. The overall improvements of the facilities by adapting Water-cooled stoker and other related systems contribute to reduce the maintenance cost very much and could be confirmed as a technology to be able to satisfy both in environmentally and economically.