For CAAD better flexibility and scalability in applications, the component-based system of CAAD employ the modular design ideas to go for a variety of test requirements (including student self-test), It takes out the central and Relatively independent business of CAAD, which will be packaged in terms of the module, and different modules call each other due to the interface, while each module is composed of a number of independent submodules and components. The advantages lies in the following aspects .First of all, various modules will be flexible "assembly" in accordance with all the different requirements of the examinations,” due to the existence of externalities, the increment will surpass the functions of the module itself. The value of the division and integration has been realized during the process. ", the whole system has the same logic with the actual examination transactions. What’s more ,by setting the module’ calling permission in the same region, a variety of versions have been derived flexibly and can facilitate communication mutually for a distributed deployment systems.