XY stages driving an electron beam (EB) mastering system for high density optical recording has been designed and prototyped. This system has some unique techniques for subnanometer accuracy, i.e. super-polygon approximation for spiral writing, auto focus adjusting, highly precise position-detecting, and a 32-bit data format. The system demonstrated fine pits writing with a small size of 50x80 nm and an accuracy of position of about 1.6 nm (σ) in a rotation direction. We confirmed that the mastering system can be applied to fabrication of 40 Gb/in 2 fine pit patterns. Furthermore, this system has the potential to write a fine pit pattern of over 100 Gb/in 2 .