With the increasingly diverse and personalized demands of customers， the service innovation of frontline employees has emerged as an essential foundation for fulfilling customer needs and promoting sustainable development of enterprises. However， currently， frontline employees primarily rely on predefined service rules to provide services， demonstrating a lack of initiative for innovation. Drawing on the motivational information processing theory， it constructed a theoretical model of the cross-level effect of enterprise-union coupling relationships （EUCR） on frontline employees’ service innovative behavior. Cross-level regression analysis was conducted based on two-stage matched data from 63 service enterprise managers and 491 frontline employees. The results indicate that： EUCR exert a significant positive influence on frontline service innovative behavior， and this effect is transcend the singular impact of enterprise management practices； EUCR affect the service innovative behavior of frontline employees through cognitive motivation in the form of harmonious innovation passion and social motivation in the form of customer perspective taking. Harmonious innovation passion strengthens the depth of frontline employees’ processing of customer demand information by frontline employees， so as to positively moderates the mediating role of customer perspective taking in the relationship between EUCR and frontline employees’ service innovative behavior. Customer perspective taking expands the scope of information search for frontline employees with harmonious innovation passion， so as to positively moderates the mediating role of harmonious innovation passion in the relationship between EUCR and service innovative behavior. The conclusion enriches the theoretical basis for frontline service innovation， and provides a new avenue for enterprises to promote service innovation of frontline employees.