Abstract: This paper provide a new way which analyzes the characters of in-degree of every phases in the process of cross-disciplinary in patent citation networks.To clarify this idea further, a example of 8608 patents of graphene technology is proposed to construct patent citation network. The results show that the in-degree distribution follows the power law when the technology is applied in the same field. And preferential attachment mechanism works well. While The in-degree distribution disobey power law when the technology is applied across various fields. The preferential attachment doesn’t work so well. The method proposed is helpful to identify a technology’s application of cross-disciplinary. Which will give suggestions to enterprises for R&D and government for policy made. Thus it will promote the multi-domain application of technology.