The rapid advancement of Artificial Intelligence (AI) has introduced new possibilities in urban and architectural conceptual design, reshaping traditional workflows and creative methodologies. This thesis starts by literature review and case studies to set a theoretical background. After that it investigates the application of some mature AI tools, including ChatGPT, DALL·E, and Stable Diffusion as an example, within the context of a design competition, which focused on urban and architectural issues. This thesis studies how AI can support conceptual design. It focus on how AI may change the traditional design process in urban and architectural projects. Meanwhile, It also examines the limits of current AI tools.