Gear-driven main motion of gantry-type machining centers have characteristics of high rigidity and large torque. Fixed bridge provides good stiffness. Two kinds of square ram dimensions are used for standard supply i.e. square ram with section area of 350×350mm and that of 420×470mm. The ram is intergrated into headstock with long travel guiding inside, its motion has been balanced all the time under help of hydraulic oil cylinder to obtain small kinetic inertia, flexiable movement and good stability. The spindle head is designed available for matching with vertical and horizontal spindle, among which the horizontal one can realize 5°×72 rotation. Both the vertical spindle and the horizontal spindle have functions of auto tool changing, as well as five-side performance. Machines of this series are ideal equipments for processing key work-pieces such as machine bed, column, box and for work-pieces with higher accuracy as well.