From the perspective of job characteristics, this article discusses the influencing factors of knowledge-sharing behavior of knowledge workers based on the Theory of Planned Behavior. The analysis of 349 knowledge-based employees’ survey data using SPSS 22.0 and Mplus7.0 software shows that: The skill variety, task identity, task significance, task autonomy, feedback, which are five core dimensions of job characteristics, are significantly positively related to the knowledge sharing willingness and behavior of knowledge workers. Knowledge workers’ willingness to share knowledge is not only significantly positively related to their knowledge sharing behaviors, but also mediates the relationship between the five core dimensions of job characteristics and their knowledge sharing behaviors.