Knowledge management (KM) has become an important term in the construction industry. Knowledge management involves creating, securing, capturing, coordinating, combining, retrieving, and distributing knowledge. Most know-what, know-how, and experience exists only in the minds of individual participants during the construction phase of construction projects. The knowledge can be reused and shared among the involved engineers and experts to improve the construction process and reduce the time and cost of solving problems. Sharing and reusing knowledge depends on acquiring and preserving of both tacit knowledge and explicit knowledge as the property of a corporation. This study addresses application of knowledge management in the construction phase of construction projects and proposes a construction activity-based knowledge management (ABKM) concept and system for general contractors. This chapter proposes a practical methodology to capture and represent construction project knowledge by using knowledge maps. Using knowledge maps, users can get an overview of available and missing knowledge in core project areas and take appropriate management in tacit and explicit knowledge. Also, a Web-based system is developed to assist and present project-related knowledge by providing keyword and map search on the Internet environment. The ABKM system is then applied in a case study of a construction precast building project in Taiwan to verify our proposed methodology and demonstrate the effectiveness of sharing knowledge special in the construction phase. By effectively using information and Web technologies during the construction phase of a project, knowledge can be captured and managed to benefit future projects. The combined results demonstrate that an ABKM-like system can be an effective tool for all experts and engineers participating in construction projects by utilising the knowledge management concept and Web technology.