Health data sharing can benefit patients to self-manage the challenging chronic diseases out of hospital. The patient controlled electronic Personal Health Record (PHR), as a tool manages comprehensive health data, is absolutely a good entry point to share health data with multiple parties for mutual benefits in the long-term. However, sharing health data from PHR remains challenges. The sharing of health data has to be considered holistically together with the key issues such as privacy, compatibility, evolvement and so on. A PHR system should be flexible to aggregate health data of a patient from various sources to make it comprehensive and up-to-date, should be flexible to share different categories and levels of health data for various utilizations and should be flexible to embed emerging access control mechanisms to ensure privacy and security under different sceneries. Therefore, the flexibility of system architecture on the integration of existed and future diversifications is crucial for PHR’s practical long-term usability. This paper discussed the necessity and some possible solution, based on the reviewed literatures and the experience from a previous study, of flexible PHR system architecture on the mentioned aspects.