Patent contains lots of information about background, technology, function and so on, which plays an important role in innovation field. Patent is something created by innovation knowledge, at the same time, it promotes us to make more use of innovation knowledge and break the inherent thinking and the limitation of knowledge, which inspires designers in the process of product design. From the term of innovation design, a new method for extracting innovation knowledge was proposed based on combination feature and maximum entropy classifier. The natural language processing was used, patent terms recognition algorithm was given, and word feature and syntactic feature of the closed package tree in the shortest path were jointed to compute the middle result. After that, the maximum entropy algorithm was applied to extract innovation knowledge based on semantic analysis and mark the attributes of knowledge. The results show that the combination feature can effectively deal with patent issues which need to be solved, and the relationships among the semantic role of knowledge innovation about target function, function principle and position feature in the technical scheme.