Along with the development of market and professional development of building, full course project consultation mode is becoming the leading tendency. As the key part of the mode, cost management decides the investment yield and the construction quality control. Starting with the development background of full process engineering consultation, the basic concepts of consultancy and cost management are given, and the outstanding problems that exist in present cost-management practices, such as inadequate machinery, lack of co-ordination, and lack of expertise are discussed, as well as the basic principles for optimizing cost management, as well as suggesting a way to improve the quality of the system, as well as training personnel. The results of this study can be used to improve the quality of cost control and to cut down the cost of the whole course of the project.