Enhancing political trust is an important manifestation of China’s ability to modernisation national governance in the media age. In the context where unofficial media has a crowding-out effect on official media, building political trust effectively becomes an important foundation for promoting the construction of a national governance system. This study employs the 2015 survey data on social consciousness of netizens and constructs a moderated mediation model using the bootstrap method, with subjective well-being as the intermediary variable and official media use as the moderating variable, to empirically explore the influence of unofficial media use on political trust and its underlying mechanism. The results reveal that unofficial media use significantly and steadily deconstructing political trust. In terms of the mechanism of transmission, subjective well-being is an important channel used by unofficial media use to deconstruct political trust, official media has a positive moderating role in the impact pathway of subjective well-being on political trust. Further research finds that unofficial media use has a stronger impact on trust in the central government, court, and police, compared to trust in township governments. Weibo or online communities and overseas media can deconstruct political trust, however, gossip or chatting with friends can construct political trust. In general, this study provides theoretical basis and empirical experience for how to enhance government trust and ultimately promote the construction of national governance system, given the increasing influence of unofficial media. Meanwhile, the research results also provide some reference value for countries with similar backgrounds to China.