Work engagement is regarded as the key driving force for the survival and development of an organization, and the current primary healthcare worker group is in an unstable vulnerability scenario at this stage, so how to stimulate the work engagement of primary healthcare workers and reduce their vulnerability is one of the urgent challenges in the field of organizational management. Based on resource conservation theory, this paper explores the impact of primary care workers’ vulnerability on work engagement. Through a survey of 887 valid questionnaires, the study finds that: primary care workers’ vulnerability can significantly and negatively affect employees’ work engagement; work motivation plays a partially intermediary role in the relationship between primary care workers’ vulnerability and work engagement; and opportunities for career growth not only negatively regulate the relationship between primary care workers’ vulnerability and work motivation, but also negatively regulate the relationship between primary care workers’ vulnerability and work motivation. Career growth opportunities not only negatively moderated the relationship between primary care worker vulnerability and work motivation, but also negatively moderated the indirect effect of primary care worker vulnerability on work engagement through work motivation. The results of the study help to understand the current situation of vulnerability faced by primary care workers and shed light on the mechanism of vulnerability’s influence on work engagement, as well as provide effective management insights for managers in the health care sector.