This is a systematic review of empirical studies on graduate students' research motivation, a key factor for improving their research performance. A total of 57 articles and conference papers between 1993 and 2023 were identified through the thorough search process and quality assessment, and their research categories and themes, theories, and methodologies were synthesized. Based on this review, a Graduate Students' Research Motivation Model (GSRMM) was constructed, highlighting three main categories: antecedents, consequences, and mediating roles of graduate students' research motivation. The results of the study showed that manipulable antecedents have been extensively explored, but immutable antecedents, consequences, and the mediating roles of research motivation remain underexplored. Self-efficacy theory emerged as the dominant framework in the existing studies. Quantitative research design by means of self-report questionnaires dominated the current studies, which warrants a move towards alternative research measurements. This comprehensive review provides a deeper understanding of graduate students' research motivation and also suggests new avenues for further exploration in this field.