Abstract: Cameras in courtroom is a judicial reform to implement the principle of open trial in depth, and to enhance the credibility of the justice, which means we should pay more attention to it. This article orients the reform’s legitimacy, and focuses on its theoretical basis: firstly, the third person effect from the perspective of communication study discusses the effectiveness of cameras in courtroom on the potential offender; then, the principle of public participation from the perspective of political science analyzes how broadcasting live promotes judicial justice in the public education effect; finally, the principle of open trial from the perspective of jurisprudence explores the role of broadcasting live in deepening the principle.