The cognitive system of human beings is formed in the process of discovering， understanding and exploring the world. As a part of the cognitive system， taxonomic relations and thematic associations are complex but also organized. The author mainly discusses the definitions of taxonomic relations and thematic associations， and analyses their main influencing factors， in order to put forward personal opinions and prospects for the research and development of conceptual connection.
　　1. Taxonomic Relations
　　Taxonomic relations refer to the conceptual connection formed by organizing things according to the abstraction degree of things. In the cognitive process， people form a global concept for many individuals with common characteristics or similar attributes， and then establish corresponding taxonomic relations based on them among things. For example， the relationship among “Persian cats”， “cats”， “mammals” and “animals” belongs to taxonomic relations.
　　2. Thematic Associations
　　Thematic associations are the external relationship among things， which means that objects， events， people or other entities have co-exist relations in time， space or function with each other （Lin， 2001; Murphy， 2001）. Things that are in thematic associations often occur in the same event or situation at the same time， but they have a common theme.
　　If two things are in thematic associations， people naturally associate one of them with the other. For example， “rabbit” and “radish” have no common characteristics or similar attributes in both external shapes and internal functions， but they have close external relations. People can’t help associating “radish” with “rabbit”， which is a typical kind of thematic associations.
　　3. Influencing Factors of Taxonomic Relations and Thematic Associations
　　3.1 Language
　　At present， the exploration of language as one of the influencing factors mainly focuses on children. When children begin to learn the names of things， they seem to understand the implicit meanings in words and form a certain sense of concepts. For example， they may refer to “cats”， “horses” and “chickens” as “dogs”. They classify the basic level concepts into functional and perceptual categories in the learning process， so that the initial general concepts are refined gradually， and then they organize concepts hierarchically （Nelson， 2000）. Moreover， When children learn some relational concept words， they often began to regard these words as names of entities and then gradually acquired relational concepts through analogy under the guidance of language （Sell， 1992）. 　　3.2 knowledge and experience
　　Knowledge and experience can help people deduce the important characteristics of a concept. If learner’s knowledge and experience can highlight the characteristics of conceptual members， learners will quickly grasp the concepts to be learned; otherwise， they need lots of practices to master the corresponding concepts. Proffitt， Coley and Medin （2002： 812） found that forestry experts used professional knowledge instead of general taxonomic concepts to judge and infer tree species. In other words， they first applied thematic-related expertise while common knowledge based on taxonomic relations is secondary.
　　4. Conclusion
　　Based on previous studies， this paper introduces taxonomic relations and thematic associations and discusses the influence of language as well as knowledge and experience on them. In the future， the author will continue to explore and improve the study. For example， we can try to explore the influence of different second language proficiency on them.
　　References：
　　[1]Lin， E. L， Murphy， G. L. Thematic relations in adults’ concepts[J]. Journal of Experimental Psychology： General，2001.
　　[2]Nelson， K. Global and functional： Mandler’s perceptual and conceptual processes in infancy[J]. Journal of Cognition and Development，2000.
　　[3]Proffitt， J. B， Coley， J. D， Medin， D. L. Expertise and category-based induction[J]. Journal of Experimental Psychology： Learning， Memory