At present, the cost problem is the main concern that restricts the development of assembled prefabricated buildings. With the integration of design, procurement and construction, the EPC mode has the characteristics of informatization, integration and specialization, which provides a direction for the project management and cost control of prefabricated buildings. Considering the increasing needs of prefabricated buildings and solving its cost problem, this paper studies the cost influencing factors of prefabricated building components from the perspective of EPC and according to the characteristics of prefabricated concrete buildings. Through the basic theory, this paper obtains 14 representative influencing factors and establishes ISM model to analyze the relationship between cost factors and obtain the surface direct factors, intermediate dynamic factors and deep leading factors affecting the cost. In this paper, the method MICMAC is used to analyze the dependency and driving force of cost factors and get the inner relationship between the factors is obtained. Finally, targeted suggestions are made to the above issues to provide direction for promoting prefabricated buildings.