This paper studied the information diffusion process in Microblog network in China. By empirical data collection we proposed a new diffusion model of concept based on mean-field assumption. The model is developed on BA model and under the mean-field assumption, by which we divide the users into three groups: "non-enlightened" group, "enlightened and committed" group and "enlightened yet non-committed" group. Experiments show that the lager the "enlightened yet non-committed" group to an opinion, the slower the diffusing process, and the more rational the network would be. And the transmission ways is insignificant referring the result.