Based on self-regulation theory and social exchange theory,the "cognition-motivation-behavior" analysis framework was used to explore the mechanism and boundary conditions of the effect of overqualification on emotional labor. The empirical test based on the valid questionnaire survey data of 339 respondents in the service industry draws the following conclusions：Over-qualification has a positive effect on deep impersonation behavior, the acquired impression management motivation plays a full mediating role between overqualification and deep impersonation behavior, and customer relationship value can strengthen the positive effect of overqualification on acquired impression management motivation.Over-qualification has a negative effects on surface play behavior, defensive impression management motive in over qualification and surface play a fully mediating role between overqualification and surface play behavior the customer relationship value can relieve over qualification for defensive impression management motive of negative influence, at the same time over qualifications have indirect effects on surface play behavior.