Under the “one-country, two systems” policy, three definitions of terrorism exist in China, which makes the inter-regional assistance in preventing and combating terrorism more difficult in the absence of mutual legal assistance agreements. Therefore, a harmonised definition of terrorism is proposed. This article first introduces the background as to why a harmonised definition of terrorism is needed in China, and then compares the objective element (the prohibited conduct), the subjective element (the specific intent) and the exception to the three definitions of terrorism. This is followed by an analysis of the concrete proposal of a harmonised definition of terrorism in China, taking into account international definitions and national definitions. The proposed definition aims to strike a balance between the need to combat terrorism in the Chinese context and human rights protection.