This paper suggests an approach for providing the dynamic federations of clouds. The approach is based on risk assessment technology and implements cloud federations without consideration of identity federations. Here, for solving this problem, first of all, important factors which are capable of seriously influencing the information security level of clouds are selected and then hierarchical risk assessment architecture is proposed based on these factors. Then, cloud provider’s risk priority vectors are formed by applying the AHP methodology and fuzzy logic excerpt type risk uation is carried out based on this vector.-This paper suggests an approach for providing the dynamic federations of clouds. The approach is based on risk assessment technology and implements cloud federations without consideration of identity federations. Here, for solving this problem, first of all, important factors which are capable of seriously influencing the information security level of clouds are selected and then hierarchical risk assessment architecture is proposed based on these factors. Then, cloud provider’s risk priority vectors are formed by applying the AHP methodology and fuzzy logic excerpt type risk　uation is carried out based on this vector.