Abstract: The frequent occurrence of public welfare trust crises on social media have affected the development of public welfare undertakings and the enthusiasm of the people for participation. In order to improve the governance capabilities of governments and institutions, the diffusion mechanism should be deeply analyzed. In order to describe the controversial characteristics of the events, considering the polarity of emotion and the difference of topics, this paper proposes a measurement method for the controversy of public benefits trust crises events on social media. By considering the complex contagion theory, the contagion process measurement methods such as initiation ability, social strengthening and social kinship can be constructed, which can express the characteristics of online public opinion dissemination and verify its impact on the controversy. Then taking the " Wu Hechen event” and “Qinghai earthquake event” on Sina Weibo as an example, the empirical research was carried on and found that the degree of controversy of public welfare trust crises has a large fluctuation .Moreover, the changes of the initiating ability, social kinship and complexity propagation of public welfare trust crises are significantly different from each other. Finally, through the QCA method, the action mode of complex diffusion feature on dispute degree is found.

Key words: Public welfare trust crisis, Complex diffusion, Public opinion communication, Social media, Measurement of controversy