Information technology has enhanced international dialogue, exchange and trade and facilitated global flow of goods and services. Key infrastructures which withhold internal stability and operation of country provide convenient services including electricity, water, transportation and financial system. Digitalized infrastructures can promote economic prosperity, strengthen military capability, and enhance the transparency of government. Nevertheless, while the world is increasingly relying on cyberspace, it is likely that loopholes can be generated along with the development of information technology. Thus, key infrastructures can be devastated by cyber attacks and pose great challenges to national security. The US acknowledge the scope of cyberspace challenges which covers the fields of military, economy, livelihood, and even international affairs. The cyber security has also been considered as one of the most serious threats to national security.Through the practicing process for tackling the challenges of cyber security, this article analyzes the implications of cyber security to the US, and generalizes the trend of cyber threats that the US is currently facing. Secondly, it illustrates the experiences of how America protects its cyber security, including innovation of organization, promotion of public-private partnership, and strengthening the efforts of intelligence gathering and counter-intelligence efforts. Finally, it is worth learning the lessons from American's cyber security protection in order to establish a comprehensive and forward-thinking strategy and to build new circumstances for security works. These efforts are able to enhance the efficacy of Taiwan´s security works so national security can be ensured.