Self-Adaptive software in open and distributed environments (especially the Internet) has been widely researched in academia and industry. However, software entities scattered on the Internet are independently developed and deployed by different organizations, and they autonomously take actions on behalf of their owners. They can no longer be considered passive and manageable. In the construction of self-adaptive software systems in open and distributed environments, constituent elements should be modeled and designed as autonomous computing entities, and the adaptive logic of systems should be encapsulated into constituent elements. Existing researches on autonomous computing entities are still insufficient in self-adaptive policies’ in online customization and dynamic evolution. Therefore, this paper proposes an autonomous component model, which supports self-adaptive policies’ in online customizing, by which components can gain new policies or behavior modes at runtime. Meanwhile, this paper implements a self-adaptive mechanism based on dynamic quality evaluation, by which components can evaluate the policies and select the best policy to improve their qualities of service at runtime. Finally, the paper provides some implementation details of the proposal and an experiment, which demonstrates the process of self-adaptation based on dynamic quality evaluation and the process of online policy customization.