Abstract: To deal with the problem that much information is unknown and the experts will hesitate about the point value of evaluation, When information security risks are assessed, improved hesitant fuzzy set for information security risk assessment is proposed.The method's idea is transforming the actual estimation into the decision matrix of the fuzzy set and calculating the weight of each underlying index.Then, the decision matrix is weighted by the weight of underlying index and expert.The result is calculated using fractional function.This method is used to solve the problem that the fuzzy nature of the scheme and expert's decision-making in the information security risk assessment process which cannot be fully reflected and make the information security risk assessment more objective and practical.The example analysis shows that the proposed algorithm is Reasonable and effective.