Based on dynamic capability theory and legitimacy theory, a theoretical model is constructed to examine how big data capability, through the mediation of knowledge dynamic capability, drive business model innovation under the moderation effect of innovation legitimacy. The analysis is conducted using regression analysis and fuzzy set qualitative comparative analysis (fsQCA) on survey data from 302 enterprises that have already implemented big data application practices. The study finds the following four conclusions. (1) Big data capability has a significant positive impact on business model innovation. (2) Dynamic knowledge capability partially mediates the relationship between big data capability and business model innovation. (3) Innovation legitimacy positively influences business model innovation and positively moderates the relationship between big data capability and business model innovation. (4) Through further qualitative comparative analysis, two causal paths that influence business model innovation are identified.