Drawing on corpus-based Critical Discourse Analysis (CDA), this study addresses the research questions relating to the government interpreters' alignment vis-a-vis their institutional employer and (re)construction of China's discourse and image as civil servants at China's Premier-Meets-the-Press conferences. A typical discursive event, the interpreter-mediated and televised press conferences provide the Chinese premier the opportunity to answer journalists' questions on various topical issues, and, in doing so, present China's global diplomacy and domestic developments to a global audience. Featuring relatively comprehensive coverage of discourse at different levels, Fairclough's (1989; 1992; 1995) three-dimensional model is employed as a general theoretical framework. I argue, however, that his CDA model needs to be further enriched and adapted in a way that accounts for the dynamic and bilingual interpreter-mediated event. Given the triadic nature of the press conference setting (featuring the interactions between the Chinese officials, interpreter and journalists), the Bakhtinian concept of dialogised heteroglossia is discussed, which highlights the negotiated nature of interpreting where the interpreters are caught up in an ideological 'tug-of-war' between the centripetal force represented by the Chinese government and the centrifugal force exerted by the (foreign) journalists who pull away from the centre and challenge Beijing's official narratives. Furthermore, (political) interpreting is conceptualised as a (re)contextualisation process at a macro-level, which necessarily involves numerous micro instances of decision-making, stance-taking and possibly shifts when rendering information into the sociopolitical, cultural and linguistic contexts of the TT. Proposed as an enrichment of Fairclough's framework, these macro-level conceptualisations permit an empirical analysis of the interpreters' alignment and (re)construction of China's discourse and image, focusing on ideologically salient shifts in bilingual comparative CDA. For more systematic and objective analysis, the mixed-methods approach of corpus-based CDA is operationalised on 20 years of press conference data (1998-2017) to explore the interpreters' agency and discursive mediation at various levels (e.g. lexical, collocational and diachronic) and from different perspectives (self-referentiality, China's discourses concerning reform and opening-up and its core national interests, China's discourses on its past achievements, current conditions, future actions, and China's discourse on people). The findings suggest that the government-affiliated interpreters do actively mediate in the process through a variety of linguistic and discursive means (e.g. foregrounding, ideologically salient additions, mediation of self-referential items and modality). Such interpreter agency points to their crucial role in communicating beyond national borders, (re)telling the 'Chinese story' and in the international news and knowledge (re)production, (re)construction and dissemination processes in our increasingly globalised and mediat(is)ed world (e.g. the interpreted discourse into English is often further mediated and quoted verbatim by such media outlets as BBC, CNN and The Financial Times). This interdisciplinary study makes a solid contribution to the hitherto under-explored area of interpreter-mediated interaction in a political and institutional setting and enriches scholarship in related areas of CDA, corpus linguistics, discursive psychology, media and communication studies, the political sciences and Chinese studies.