The authors present an analysis which concludes that most e-health system are packaged for large-scale access through cloud-based services shared in a real-time service deployment environment. The service, which has already been deployed in the clouds for e-health construction, needs to instantly change itself in order to enhance the usability for the patients, especially for the dementia patient monitoring system. The evolution for the service in cloud-based systems can be driven fundamentally based on the service function improvement, quality of service improvement, and service collaboration improvement, which can greatly enhance the usability of the dementia patient monitoring system and dynamically enlarge the life-cycle of the current service system in clouds without replacing the reusable service components. The quality of service evolution of the dementia patient monitoring system is essential because the system reliability and instant messaging sending ability is needed in the dementia patient monitoring system. The system should be as reliable as possible for its undertaken the people's life and healthy ensure for all those who use the system.