中文摘要：

自媒体的崛起使普通公众得以实现从传播客体向传播主体的转变，为公众与政府直接对话提供了可能，也使得公众对政策议程的设置能力大幅提升。本文试图探究新媒体时代下公众议程、媒体议程、政策议程的形成及三者间的互动机制，揭示新媒体为公共政策形成模式带来的新改变。本研究以天津“8．12”爆炸事件为案例，选取研究时间段内发布的741条相关话题微博以测度公众议程，选取天津市政府召开的十四场新闻发布会内容以测度政策议程，利用文本分析法分别获取公众议程与政策议程情况。研究发现，新媒体背景下，决策者借助大众媒体对公众议程进行有效设置的传统正在被颠覆，公众议程对政策议程直接设置的能力大幅提升，大众媒体则充当了舆论监督的补充力量。

英文摘要：

The new media era is witnessing the prosperity of the so-called ＂WeMedia＂ which allows the public to voice themselves online spontaneously. People with access to the Internet are enabled to generate their very own agenda free from the hierarchal one settled by the official media. Consequently, the traditional agenda building theory treating the mainstream media as the monopolistic ＂opinion maker＂ is challenged somehow. This research aims to highlight the transformations that take place in the chain of agenda building by investigating the influences WeMedia have on the process of agenda building of the governmental policy. Taking ＂Tianjin＇ s 8.12 bomb incident＂ as the case, this paper will focus on the questions of how WeMedia have enabled the agenda to be heard and exerted on the agenda building of the government＇ s press meeting hence.