本文以优酷网的一则公益广告视频及其形成的传播单元为研究对象，分析用户在互联网平台自发传播公益广告的特征及用户参与行为，并结合中国公益广告运营模式中公众参与公益广告活动积极性不高的现象，讨论当公益广告借助互联网平台进行传播时，互联网用户在传播过程中的互动参与是否缓解了公益广告活动的公众参与积极性问题。研究发现，由于互联网传播时空的广泛性、后现代语境下的颠覆以及对抗式立场的常态化等原因，当前互联网用户参与传播公益广告的行为是滞后的、被局限的、反抗的，这并不能与协商式的公众参与相等同。笔者认为，唯有从现实中加以改善，即在公益广告的整体运营过程中有机地融入公众才能解决问题，进而避免用户自发传播对已有传播效果的消解效应。

This paper takes a PSA video in Youku as the study case to analyze the characteristics of netizens’ spontaneously initiating communication and participation behaviors, combining with one of the main problems in current Chinese PSA model, namely the lack of public participating enthusiasm during the whole process. It finds out that, as a result of the wide communicating time and space, subversion under the context of postmodernism and normalization of the oppositional code in internet, the participation and interaction of internet technology could not solve the lack of public participation in the PSA model as many optimists expected. It claims that only by improving from the reality and integrating citizens organically during the whole operating process could the problem be solved and the reduction effect to traditional channel be avoided.