The invention relates to a CNC (computer numerical control) rotary clamp of a machining center. The CNC rotary clamp comprises a main clamp, a CNC index head, a tailstock and a workpiece clamp. The main clamp is elongated; the CNC index head is connected to the head of the main clamp; the tail of the main clamp is rotatably supported on the tailstock. The front surface of the main clamp is provided with a plurality of first mounting holes evenly distributed along the length of the main clamp. The workpiece clamp is provided with a second mounting hole. The workpiece clamp is fixed to the front surface of the main clamp through screws mounted in the first mounting holes and the second mounting hole. The CNC rotary clamp is simple in structure, firm to mount and flexibly adjustable and helps improve machining performance and precision of a four-axis linkage vertical machining center.