Under power market environments, generator companies and power users are economic decision-makers and the ISO is the security decision-maker. The non-unique solution of security decisions may result in unfairness. At the same time, more and more power systems are operating near their security limits, thus the influence of uncertainty factors to security can not be ignored. To solve the above problems, the presented security pricing model in this paper suggests that security prices are calculated and released, which inducts and excites the market-participants separate decision-making, thus system security is maintained. Influences of the uncertainties of power loads and fault parameters to system security are taken into account. Furthermore, the system security and economy are unified in the model.