Since the release of Shandong vaccine incident in March 2016，the event continued to ferment and draw wide attention from the society. On the one hand，the event was closely related to public life and spreading rapidly and affecting a wide range of sectors. On the other hand，reports and public opinio about this event are constantly superimposed，reverted and evolved on social media such as WeChat and Microblog，continuously stimulating public nerve. The health risk caused by issue vaccine and the public trust crisis caused by vaccine incident formed a storm center of risk. This thesis chooses Microblog as main research object，discusses in new media context，how the risk issues are formed，influenced and adjusted to bias and how they are dissolved and replaced while spreading. In the steering od risk issue，who controll discourse power？Finally，a review is made on the responsibility and defect of media in the reporting process.