There were 11398 journals were included in Journal Citation Report from Web of Science in 2015, including about 44.47 percent of journals included by multiple disciplines, which indicates interdisciplinary is a common phenomenon. The number of cross journals among different disciplines reveals the role of journals in the interdisciplinary, which can be used to analysis interdisciplinary. This paper proposes a Cross-Discipline Vector Space Model for quantitative analysis of the degree of interdisciplinary. Through calculating the relevance among discipline, we obtain the pattern of interdisciplinary, which could provide scientific advice to promote the development of disciplines and scientific research.