The optimal software as a service (SaaS) selection based on Quality of Service (QoS) is still challenging because user rating with fuzziness and randomness makes QoS uncertain and decision-making hard.This paper presents a SaaS decision-making method based on cloud model (SDM_CM) to solve the above difficulties for the first time.It includes two main steps:(1) Converting the rating QoS criteria to the cloud model QoS criteria by using the backward QoS cloud generator.(2) Proposing a multiple attribute decision-making algorithm based on cloud model

which draws on the effective and common multiple attribute decision-making algorithm (technique for order preference by similarity to an ideal solution

TOPSIS).The last

a set of experiments demonstrate the benefits and effectiveness of our approach.