Objective To explore the motivation and influencing factors of postgraduate education pursuit among in-service nursing postgraduates, so as to provide references for developing targeted interventions to support academic advancement and career development of nursing staff. Methods A descriptive qualitative study was designed, and 16 in-service nursing postgraduates from seven grade A tertiary hospitals were selected using purposive sampling for semi-structured interviews. Thematic analysis was used to analyze the interview data. Results Three themes and 14 sub-themes were identified: a multidimensional driving structure of motivation for postgraduate education pursuit, including intrinsic drivers (self-efficacy, career aspirations), extrinsic drivers (social environmental awareness, career development pressure, risk control), and policy environment drivers; support system (foundational personal capabilities, motivation maintenance mechanisms, social support networks); and constraints (time and resource allocation challenges, psychological and emotional challenges, external conditional limitations, personal capability shortcomings, physiological constraints). Conclusion The decision to pursue postgraduate education and the preparation process for in-service nursing postgraduates are influenced by complex multi-level factors at the individual, organizational, and social levels. Nursing administrators and educators should accordingly establish supportive environments and develop personalized training programs to effectively facilitate further academic advancement and career development for nursing staff.