Nowadays, how to make a human-computer interaction system which can take into account large-area display, high precision tracking and multi-user operation at the same time is a hot research topic. This paper presents a novel low cost pen-based projective interaction system that can write or draw like writing brush. The system is composed of infrared scanning projector, digital pen, projector, screen, wireless receiver module and computer. The infrared scanning projector is designed to achieve fast projection, which is to track the pen's two dimensional location accurately along with the digital pen. The system has the advantage of multi-user supported, high tracking precision, and has the function of identity recognition and writing calligraphy.