Core technology patent early warning is the key part of enterprise patent early warning. After introducing the importance of core technology, this paper analyzes the instance of the warning source and warning intelligence in different life cycle period about the core technology patent early warning according to technology life cycle theory, and divide the warning source to four dimensions: technology entering threat, technical position threat, technology value realization threat and technology direction changing threat. After that it suggests that there are three important factors determine the degree of core technology patent early warning, that are technology, market and environment. On the basis of that, this paper builds the evaluation indexes system of core technique patent early warning further, and appraises the patent early warning grade by extenics and suggests enterprise should judge the situation and take corresponding measures according to this degree at last.