To solve this problem, this paper designs and implements a geometric teaching system based on PUI (Pen User Interface), and applies technique of bidirectional geometrical constraint to this system.

For electricity modernization of education and carrying out interaction teaching, wireless pointer based on HID (Human Interface Device) class should be designed.

Software have direct-viewing and friendly graphic interactive interface, uniform style. It offer dynamic navigation of teaching content, have strong interactivity and adaptability, manipulate simply.