This study examines the key strategic determinants influencing cross-border e-commerce (CBEC) performance among firms in China, with a particular focus on the moderating role of firm size. Drawing on empirical evidence, the research investigates how five core drivers marketing and promotion, regulatory and compliance practices, technological infrastructures, partnerships and collaborations, and the global e-commerce environment contribute to performance outcomes in international digital trade. Guided by a quantitative research design, data were collected via structured questionnaires from a purposive sample of 397 Chinese firms engaged in CBEC. Measurement validity was confirmed through reliability assessments, with Cronbach’s α values exceeding 0.82 across constructs. Structural equation modeling (SEM) revealed that all five strategic drivers significantly impact CBEC performance. Furthermore, firm size was found to moderate these relationships, strengthening or attenuating the effects of individual drivers depending on organizational scale. The findings highlight the importance of aligning digital strategies with firm capabilities and underscore the necessity for size-sensitive interventions in cross-border trade initiatives. This study contributes to the growing literature on digital internationalization and offers practical guidance for policy formulation and managerial strategy in China’s evolving e-commerce landscape.