This paper is a work scheduling for design of piping Department of chemical plant using accumulated curve. Accumulated curve prepared by analysis of performance data, collected executed manhours for chemical plant of "D" Company during the past two years. It compared scheduled manhours with actual used manhours up to six months, put into the form of figures and charts the results can he summarized as below; 1) It can he found an important factor of critical control thus piping department got 30% of total scheduled menhours. 2) A plan of manpower mobilization can be scheduled before work starting. 3) Project progress can he found easily as put into the form of figures and charts for schedule to actual.