Educational technology is a fast-growing and increasingly developed subject in education during the past 50 years. The focus of the development of its theories and research is oriented into the methods and effectiveness of its implementation. This presentation is reviewing various educational technology related theories, exploring and discussing up-to-date theoretical research and applications. The related theories not only cover those mainstream and influential ones, such Behaviorism, Cognitivism, Constructivism, and Multiple Intelligence, but also include those extended and popular theories: Anchored Instruction, Cognitive Flexibility, Diffusion of Innovations, Elaboration Theory, Experiential Learning Theory, Script Theory, Situated Cognition and Symbol Systems Theory. The application is mainly to discuss the related theories and research in educational technology and pedagogy of DL instruction through blackboard. The pedagogy of DL instruction includes the course designing, module delivery and objective-oriented assessment strategies.