Digital health literacy (DHL) has become a key factor in narrowing the health gap and ensuring that all people can benefit from digital health (DH) in the digital age. In the context of China, despite the rapid development of DH, significant disparities remain in healthcare resource allocation and DHL. However, current research primarily explores the relationship between DHL and health equity at the structural level and has not yet systematically explored the causal mechanisms influencing DHL and perceived health equity at the individual level. This thesis aims to fill this research gap by examining the causal path through which DHL influences perceived health equity via health decision-making.  This thesis employed an explanatory sequential mixed-method approach. In the quantitative phase, data were collected through an online questionnaire survey (N=176), and hierarchical regression analysis was used to examine the predictive relationships between DHL, health decision-making, and perceived health equity. In the qualitative phase, semi-structured interviews were conducted with 7 participants to explore the specific processes of health decision-making and its influencing factors. In the integration phase, this thesis draws on the philosophical foundation of critical realism (CR), which is gaining ground in DH research, to consider health decision-making as a causal mechanism, connecting DHL and perceived health equity, rather than seeing it as a statistical mediating variable.  Quantitative results showed that DHL significantly and positively predicted health decision-making and perceived health equity, and health decision-making also significantly and positively predicted perceived health equity. Qualitative results further revealed that health decision-making encompasses four interrelated processes: information acquisition, information comprehension, information appraisal, and action translation. Individuals’ DHL affects each process of health decision-making, while structural conditions constrain the causal power of DHL under different contexts. Integration results reveal that the impact of DHL on perceived health equity is not a linear relationship, but depends on whether the causal mechanism of health decision-making can be effectively activated under specific contextual conditions.