How to appraise the value creation from knowledge assets of firm has become a great interest topic in business management and knowledge assets management. Several approaches are proposed in the past, most of which focused on quality analysis of firm's knowledge assets in firm value. This paper tries to make a breakthrough on this topic by applying fuzzy set theory and fuzzy AHP method to construct a quantified model to measure the contribution value of knowledge assets items. Furthermore, by applying this model to study two cases. The results of two cases about value creation of knowledge assets show that this evaluation model is applicable to appraise the quality and the value creation contribution of knowledge assets in corporations. Moreover, using this model, managers can determine the level of assets matching, identify which specific knowledge assets item needs new investment, and so on. In another word, this fuzzy valuation model provides a novel tool for measuring, managing, and understanding the value creation of firm's knowledge assets.