Yin and Yang are important concepts in ancient Chinese philosophy.Western scholars have become more familiar with these two concepts recently,but for a long time almost no one considered comparing them with their own tradition such as the ancient Greek philosophy,and especially with the ideas of the Hot and the Cold in Presocratic philosophy.In this paper,I make an attempt to do exactly that,and especially make a detailed comparison between the thoughts of two ancient thinkers:Laozi and Anaximander.I discuss the thought of Yin and Yang in Laozi-who was the earliest philosopher making use of the concepts Yin and Yang-to express his cosmological thought in ancient Chinese philosophy.Comparatively,I discuss the ideas of the Hot and the Cold in Anaximander,the earlier among Presocratic philosophers referring to the Hot and the Cold as fundamental concepts used to establish his cosmological system.Through this comparison,I indicate that the similarity between ancient Chinese and Western traditions is far more significant than what people are used to imagining.