In the context of risk society, in order to enhance the social resilience to deal with various risks and crises, it is necessary to mobilize social forces extensively, which will help to improve the efficiency of public health emergencies in emergency management. This research conducted one-on-one interviews with 27 volunteers through three aspects: "the induction/hindrance of volunteer service", "the motivation of volunteer service" and "the sustainability of volunteer service", and conducted open coding, spindle coding and selective coding of text data. After conceptualization and categorization of content analysis, three levels of volunteers, volunteer service process and external influencing factors were formed. A model of influencing factors on public participation in volunteer service behavior in public health emergencies was constructed. Research has found that the core factors affecting public participation in volunteer services for public health emergency are: motivation for participation, organizational characteristics, interpersonal interaction, incentive mechanisms, guarantee mechanisms, constraints, and service management. The research conclusion has some practical significance for improving the attractiveness and sustainability of volunteer services to the public, improving the quality of volunteer service work, and enhancing social emergency management capabilities.