The invention relates to a turnover mechanism used in a production line, in particular to a servo turnover machine. The servo turnover machine comprises an installation table, a motor, a speed reducer, an air cylinder, a pinion, a big gear, a base, a pressing plate gear I, a pressing plate gear II, a half-cylinder rack I and a half-cylinder rack II. The pinion is a straight gear, the big gear is a toothed crossed roller bearing, the base fixed to the crossed roller bearing is driven through the rotating and meshing motion of the straight gear and the toothed crossed roller bearing, and therefore plates can rotate. When the plates need to be turned over, the air cylinder extends out, the half-cylinder rack I fixedly connected to a telescopic shaft of the air cylinder is pulled, the pressing plate gear I meshing with the half-cylinder rack I does rotating and clamping motion, and therefore the plates to be turned over can be clamped. When a system detects that the plates are clamped, the motor is driven to rotate to the position where the plates are to be turned over, the system then controls the air cylinder to retract, the pressing plate gear I meshing with the half-cylinder rack I does rotating and opening motion, and therefore the plates can be turned over.