The disclosure provides a data sharing system and a data sharing method. The data sharing system includes a storage device and a processor. The processor executes multiple modules stored by the storage device. When a first software as a service (SaaS) application program sends a data sharing request to a second SaaS application program, a mutual trust relationship service module receives a request for confirmation of a mutual trust relationship transmitted by the second SaaS application program, so as to confirm the mutual trust relationship. When the mutual trust relationship is confirmed, the mutual trust relationship service module obtains virtual user identification data from a tenant management service module, and provides the virtual user identification data to the second SaaS application program, so that the second SaaS application program obtains data authority, and shares specific data to the first SaaS application program.