Time, cost and quality are three central objectives the manufacturing enterprises seek, but they restrict and affect each other. To analyze the relations among three objectives and achieve their exact optimization during manufacturing are the important problems which are worth researching. Based on the practice investigation and reasoning, the action mechanisms of three objectives are deeply analyzed, and their effect rules and relations are ascertained. The optimization model of time-cost-quality is set up according to their relations. The special program is designed for the integrative optimization model based on the idea of accurate calculation, and is applied to solve the optimization problem. Finally the methods put forward are applied to the instance about car part manufacturing, and a series of optimization result is obtained. Some conclusions which are valuable for the manager in enterprise are summarized by analyzing the optimization result. The instance application indicates that the model and the methods can help to make decision for production.