It is quite a while ago that software as a service (SaaS) appeared, but the view that Salesforce.com began offering CRM service in 1999 is also a big milestone for SaaS to enter the main stream is there. However, the principle of remotely using software on another company’s hardware traces back to the bureau service and time-sharing service that LEO and IBM had provided at the beginning of commercial computing in the 1950s and 1960s . SaaS is the most common form of cloud computing. The user accesses the application hosted and managed on the server in the service provider’s data center using the browser and the Internet connection. The fee is to be paid according to the usage of the service or subscription method, and there is no license purchase cost or maintenance cost like on-premise type software. On-demand type software and host type application usually refer to SaaS.