On the occasion of the 10th anniversary of the proposal of the new mainstream media strategy, this study is based on the local social context framework and communication system, focusing on constructing a scientific and systematic credibility assessment scale for new mainstream media. It aims to solve the problem that traditional evaluation tools cannot adapt to the new communication field and new mainstream media, enrich the practical exploration with Chinese characteristics, and also contribute to the further improvement of media credibility theory. This study strictly follows the scale development procedure to construct a two-factor, four- dimensional credibility scale of new mainstream media from the public perspective. Supported by relevant literature, it screens the potential measurement items of new mainstream media credibility through in-depth interviews and expert consultations; using questionnaire methods, it conducts the initial scale test with exploratory factor analysis (n=500), and determines the fitting situation of the scale through confirmatory factor analysis and reliability and validity tests (n=1723). Finally, this study constructs a credibility scale of new mainstream media covering four dimensions: “authenticity/professionalism”“national image/authority”“public value” and “broadcasting skills”. It also engages in theoretical dialogue with previous studies, exploring the continuity and development of media credibility theory.