The 2.5m optical/infrared telescope is an F/8 telescope comprising one Cassegrain foci, two Nasmyth foci and two student Nasmyth foci. This paper presents a brief description of the physical structure, conceptual design, hardware implementing measure and software structure in the positioning control system of M2&M3. The graphical user interface application (Qt) is adopted to design the software. During the full working range the M2 focus and decenter achieve the positioning repeatability is better than ±4μm and the M2 tilt is better than 10 μrad. The M3 angular positioning and locking accuracy is better than 10 arcsec and repeatability is better than 2 arcsec RMS.