Abstract: How to choose the optimal cloud service resolution,is one of the most important decisions that enterprises are facing after they decide to adopt cloud services. To solve the cloud service selection problem,based on modular system theory,a cloud service technology selection behavior model was introduced,which procedure modularity,IT dismantlability and security risks were proposed as three main influencing factors from the perspectives of enterprises' business process and IT ability. The Questionnaire and OLS(Ordinary Least Square) were applied in this empirical research. The research results showed that procedure modularity and IT dismantlability had significant positive impact on the abstraction degree of cloud service selection. That meant enterprises which had higher procedure modularity and IT dismantlability were more likely to choose high abstraction degree cloud services,such as SaaS(Software as a Service),and enterprises which had lower procedure modularity and IT dismantlability were more likely to choose low abstraction degree cloud services,such as IaaS(Infrastructure as a Service). The results also indicated that security risks could positively moderate the impact of procedure modularity on the abstraction degree of cloud service selection.