Abstract: Emergency network public opinion is not only the self-expression of public perception of social risk,but also an important reference for public risk response.After the occurrence of emergencies,the risk evolution of network public opinion shows different rules in different stages:the sudden change and regular evolution of public opinion risk in the germination period,the ripple effect in the diffusion period,and the resonance in the high rising period,and dissipation in the recession period.The generation motivation of risk evolution of emergency network public opinion is the result of multiple factors,such as inherent factors,human factors,environmental factors and management factors,including the superposition of social hidden risk and public opinion risk.Public perception risk increases public opinion transformation risk,network environment imbalance accelerates public opinion risk diffusion,and public management risk leads to public opinion risk repetition.In order to promote the prevention and control work,we should strengthen the concept of public opinion risk communication and awareness of prevention and control,improve the legal protection system of public opinion risk prevention and control,build a normal long-term mechanism for public opinion risk prevention and control,and improve the technological innovation level.

Key words: emergency, public opinion risk, evolution law, generation motivation, risk prevention and control