Abstract: China is a big citrus\|producing country. However, the citrus industry chain showed strong vulnerability under the impact of a series of external events such as Guangyuan fruitfly event in Sichuan Province in 2008.It showed important significance to study the vulnerability of citrus industry chain. Industry chain is a very complicated system, and the research on the vulnerability of the industry chain is still a very new field. Thus, study on the effect of vulnerability of citrus industry chain on the development of citrus industry was quite important. This paper was based on the brittle model of complex system, and the concept and connotation of the industry chain vulnerability were the entry points. The influencing factors of the internal instability of citrus industry chain were analyzed, and its brittleness factors were refined. Finally, the evaluation index system of citrus industry chain vulnerability were constructed．

Key words: citrus industry chain, complex systems, vulnerability, evaluation index system