Based on social exchange theory, psychological contract theory and motivation theory, the influence of contextual performance appraisal on employees' knowledge sharing is studied by means of Structural Equation Modeling. The result indicates that job dedication performance appraisal has positive effect on employees' knowledge sharing partly mediated by the motivations of submission to rules, attachment and responsibility for collectivity; interpersonal facilitation performance appraisal has not significant influence on knowledge sharing. The moderator effects of work locus of control on the relationship between teambased performance appraisal and knowledge sharing has not been found.