The series of unified empires or dynasties in the history of China (221 BC-1912 AD) have shaped the unification pattern of Chinese culture. Therefore, the eastern civilization (China) can be deemed as a unified culture. In the geographical scope of China in East Asia, there is a stable and continuous history process of one-by-one unified dynasties (empires). Between two old and new unified dynasties in the history of China, there are always chaotic (transitional) periods when several local regimes competed for the absolute power of China (the Mandate of Heaven). In these transitional periods, wars and annexations are always inevitable. Then, only one local regime will succeed in gaining that power, forming a new unified dynasty (empire). The cultural pattern is obviously different in the western world, and there are no stable unification patterns. In Europe, there were also chaotic periods, with wars and annexations. However, there is no stable pattern of unification, which means that no local regimes (countries) have unified mainland Europe. Hence, whether this process can be modeled and revealed? We believe that computational methods can reveal some laws and rules of historical dynamics. For this work, we need to solve the conditions of both the Unity and Disunity. To achieve this goal: first, we build an agent-based model of general history dynamics for the chaotic periods; second, we run the simulations to explore outcomes of the unity and disunity; last, we obtain valid solutions for both the unity of China and the disunity of the West world. It suggests that our valid solutions explain the disunity between China and Europe patterns. Moreover, we can calculate the conditional boundaries of both Unity (China) and Disunity (Europe). Thus, the unification process in human history may be universal, but the outcomes or patterns may be different under different conditions.