An optimal construction site layout planning (CSLP) can enhancing the services of the construction work to improve the work productivity and thus the costs of a project. The previous studies of CSLP centralized on the equal-area and static site layout planning, which is idealized but practical unequal- area and dynamic planning studies are limited. In order to enhance the knowledge and practices of solving unequal-area and dynamic problems, the CSLP decision-making system using ant colony optimization (ACO) algorithms is proposed in the study. The feasibility and effectiveness of the proposed CSLP decision-making system were tested and verified by two projects. The results showed that the proposed CSLP decision-making system can select a good site layout, which reduced the project costs significantly by comparing with the original site layouts. CSLP decision-making system will assist the practitioners in the construction industry to deliver construction projects in a more efficient and effective manner, thus to reduce construction costs significantly.