Application virtualization is a key technology to support the software as a service. This paper analyzes and gives out the definition of application virtualization, discusses the advantages and research status of applicatio virtualization, and points out that the current application virtualization research is mainly centred on implementation issues, but negligent of the service quality of application virtualization. From the angle of platform dependence and distributed architecture, the application virtualization can be divided into homogeneous or heterogeneous application virtualization and local or remote application virtualization. And the paper analyzes the different types of application virtualization implementation principles in detail as well as the corresponding typical application virtualization software and their characteristics. Subsequently, the paper approaches the service quality evaluation method of application virtualization from the perspective of evaluation indicators and evaluation methods. Finally, aimed at the challenges faced by the service quality of application virtualization, the paper presents the research trends in application virtualization.