The construction of the power Internet of Things（IoT）forms a real -time power market main information collection library, which provides decision-making assistance and active service to the whole power market. According to the fast fluctuation of electricity price, which makes the power retailers being taken the risks of losing profit under power IoT environment. A market insurance mechanism based on electricity price fluctuation insurance is proposed. Firstly, the electricity trading market structure based on market insurance is established, and the complex relationship between the main trading subjects is clarified. Secondly, the optimal insurance strategy of power retailers and insurance design strategy of the insurance companies are forward though the quantitative evaluation of the cost profit. Finally, a case of the market operation of power retailers in Guangdong province demonstrates the realizability and application value of the insurance mechanism transfer and the diversification of the operating risk of power retailers, which show that the proposed insurance mechanism can effectively disperse and transfer the risk of electricity price fluctuation, and reach win-win situation between power retailers and insurance companies.