Major public decision-making risks include both the risk of decision-making itself and the risk that decision-making mistakes bring to the political， economic， social， cultural，ecological，moral，technological and security fields. These risks are more conflicting and destructive. To effectively govern these risks, it is urgent to introduce big data thinking and technology to realize the diversification of governance subject, the specialization of governance content, the scientific method of governance and the democratization of governance means. In fact, because big data can drive the accurate identification, scientific prediction, accurate monitoring, professional evaluation and effective handling of major public decisionmaking risks, big data can be used to manage the decisionmaking risks of major public affairs, which can make the governance subject more diversified, content more specialized, method more scientific and means more democratic. In order to apply big data to the effective management of major public decisionmaking risk, on the basis of big data analysis, we should make clear the accurate identification method of decisionmaking risk, construct scientific prediction path and accurate monitoring platform, cultivate professional evaluation system, and rationalize the ideas of effective treatment of decisionmaking risk.