With advances in information technology, various cloud computing related research and development has become a hot trend. Except the vast amount of studies and reports appearing in local magazines and newspapers, government agencies have also set up corresponding R & D projects. However, most of these studies focus on the infrastructure or platform level of the cloud. For example, the projects for Infrastructure as a Service (IaaS) include the Cloud Computing Center for Mobile Application at Industrial Technology Research Institute (ITRI), the Cloud Service and Technology Center at Information Industry Institute (III) and the already launched ¡§hiCloud¡¨ at Chunghwa Telecom Corporation. In the business side, there is TCloud Computing that does the development of both "Infrastructure" and "Platform as a Service" (PaaS). As to Software as a Service (SaaS) related research, III has gathered 10 domestic companies to participate the co-operation plans for education cloud, manufacture cloud, ¡K and practice cloud, a total of nine cloud services. However, they are all in the early stages without much success stories or usages. The study of this thesis is angled toward business needs, from the point of resource-based analysis to see how a firm will be affected if introduction of SaaS to business. In particular, we will study this subject from four dimensions, which are the competitiveness of enterprises, IT outsourcing strategy, cost structure analysis and data security technology, to identify the possible critical factors for the introduction for cloud computing services. As most people are perceived, cloud computing has a comparative advantage of cost saving over traditional approach.