Abstract: Earned Value is the most important measurement in the project cost and schedule control. This paper describes the concept and methods of earned value,and its application in the project cost and schedule control. Then, this paper tells how to forecast the likely cost to complete the project,and intruduces the concept of S-curve. Using S-curve, it's easy to present that whether the project is under-or overspent as it progress, and if the project is ahead or behind schedule. At last,this paper describes the difference between the baseline complete cost and the budget. The baseline complete cost is one of the measurement of project control, while the budget is the expected cost which the owner of the project wants to pay. The difference between the two is the contingency.