Describes how to develop the on-line help system for doctor CAD system and brings forward some general principles of designing such a system. It also gives the main idea of the design process.

Ask for help to weave the distance technique in the application, even can carry out the on-line upgrade of long range with a machine system.

With a series of experiments, it is proved that using the system can realize an off-line BCI based on visual stimulus easily, and on-line BCIs with other apparatuses' help are possible.