The pre-modern society mainly based on authority and individual trust, while the rise of modern society could be viewed as a shaping process of system trust, the expert system in particular. The ethos of trust provides impetus for social development. Yet the coming of risk makes the society step into ‘post-trust society＇. The ‘post-trust society＇ has rebuilt the characteristics of experts, the interaction mechanism and policy structure. The study of risk governance leads to a new trend. It is illustrated in three relevant dimensions： firstly, the public begin to participate into the risk perception instead of risks defined fully by the expert system; secondly, the oneway mode of risk communication mechanism has been replaced by the multiple ones; thirdly, the internal way of risk governance has shown its superiority over the external way of risk management. The multi-dimensional approaches of risk research in social sciences are beneficial for reflecting the risk communication mechanism in ‘post-trust society. And thus, it is of significance to build the social trust system in transforming period full of social risk plights, which will lead to more effective risk communication and better policies of risk governance.