This paper begins with some historical stories of the struggles between the Chinese Communist Party (CCP) and the Kuomintang (KMT). It shows that CCP's spies not only saved the party from being hunted down by the KMT in its initial stage, but also played a decisive role in winning the civil war. After the KMT government retreated to Taiwan, the CCP continued using the same tricks. The infiltration of Chinese spies in Taiwan intensified after Taiwan became a democracy and opened up the restrictions on cross-strait trade and transportation. This paper analyzes the techniques applied by Beijing to collect military intelligence, and illustrates these techniques with examples. This paper also provides some other important cases from the most recent ten years. Finally, the conclusion describes the counter measures and provides suggestions. These measures include amendments to the Criminal Code, the Act Governing Relations between the People of the Taiwan Area and the Mainland Area, the Classified National Security Information Protection Act, and the National Security Act. Beyond these amendments, this paper argues Taiwan's government must strengthen the patriotism of its citizens.