Abstract: Based on the theory of human-environment interaction，social exchange theory and social identity，this paper used AMOS22.0，SPSS20.0，Mplus7.4 and Origin 2017 to statistically analyze the survey data of 693 knowledge workers. A moderated mediation model is built to research the effect of employee engagement on knowledge sharing willingness of knowledge employees as well as the partial mediating role of organizational identity and the moderating role of person-organization fit. The results show as follows：employee engagement has a significant positive effect on willingness to knowledge sharing of knowledge employees；organizational identity partial mediates the relationship between employee engagement and willingness to knowledge sharing of knowledge employees；person-organization fit plays a moderating role in the mediating path，forming a moderated mediation model；in the moderation role，person-organization fit has a greater impact on organizational identity than employee engagement.

Key words: employee engagement, knowledge sharing willingness, organizational identity, person-organization fit, knowledge employee