The security in the cyberspace undoubtedly belongs to emergent properties in nature. This kind of emergent properties brings about severe challenges to cybersecurity. A number of efforts of research on emergent phenomena related to the security in the cyberspace have been seen both home and abroad. Up till now, a lot of significant results have been achieved by this kind of research. However, people’s knowledge of emergence in cybersecurity is still far from sufficient. For this situation, the challenges to cybersecurity are observed systemically from the perspective of emergence to promote the development of innovative ideas and theories in cybersecurity. At first, fundamental concepts of emergence in cybersecurity are revealed based on the original meaning of emergence in systems science. Secondly, challenges of emergent security to the cyberspace are explored with consideration to attacks, vulnerabilities, and defenses. Then, the state-of-the-art of research on the emergence of security in the cyberspace is analyzed in a way that it has been divided into three categories, which include descriptive research, directive research, and operational research. Finally, with the focus on fundamental theories, basic models, and practical tools, discussions are made to answer the question about how to further the study in the future in the field of emergent security in the cyberspace.