A nested numerical control rotary table, comprising a large numerical control rotary table and a large rotary table board, and further comprising a small rotary table, a small rotary table board, characterised in that it further comprises a lifting oil cylinder, a bracket, a positioning pin boss, a positioning pin, an elastic piece, a shifting pin, a clamp and a guide rail; wherein the small rotary table board is nested in the large rotary table board, the positioning pin boss is arranged at a joint between the large rotary table board and the small rotary table board, a pin hole is formed in a side surface of the small rotary table board, the positioning pin comprises a positioning pin body arranged in the positioning pin boss, a driving curved surface arranged at an outer end of the positioning pin body and a positioning pin head arranged on a side surface of the driving curved surface, the elastic piece is arranged in the positioning pin boss, and the positioning pin head may be inserted into the pin hole in the side surface of the small rotary table board under the push of the elastic piece to connect the small rotary table board with the large rotary table board; a top surface of the shifting pin is an inclined plane, the shifting pin is fixed on a side surface of the small rotary table and positioned below the driving curved surface, a top end of the shifting pin is higher than the small rotary table, the bracket fixedly connects a top end of a piston rod of the lifting oil cylinder with the small rotary table, the clamp is fixed on the bracket, the guide rail is fixed on a side surface of the large numerical control rotary table, and the guide rail is in sliding connection with the clamp; a positioning cone is arranged on the small rotary table, and a pull pin corresponding to the positioning cone in position is arranged under the small rotary table board; and is configured so that in use the lifting oil cylinder lifts the small rotary table along the guide rail through the bracket, a top surface of the shifting pin makes contact with the driving curved surface, as the small rotary table ascends, the shifting pin pushes the positioning pin head out of the pin hole so that the small rotary table board is separated from the large rotary table board, the pull pin is fixedly connected with the positioning cone, the small rotary table board is fixedly connected to the small rotary table, the small rotary table drives the small rotary table board to work, and the clamp clasps the guide rail to fix the position of the small rotary table. a lifting oil cylinder, a bracket, a positioning pin boss, a positioning pin, an elastic piece, a shifting pin, a clamp and a guide rail; wherein the small rotary table board is nested in the large rotary table board, the positioning pin boss is arranged at a joint between the large rotary table board and the small rotary table board, a pin hole is formed in a side surface of the small rotary table board, the positioning pin comprises a positioning pin body arranged in the positioning pin boss, a driving curved surface arranged at an outer end of the positioning pin body and a positioning pin head arranged on a side surface of the driving curved surface, the elastic piece is arranged in the positioning pin boss, and the positioning pin head may be inserted into the pin hole in the side surface of the small rotary table board under the push of the elastic piece to connect the small rotary table board with the large rotary table board; a top surface of the shifting pin is an inclined plane, the shifting pin is fixed on a side surface of the small rotary table and positioned below the driving curved surface, a top end of the shifting pin is higher than the small rotary table, the bracket fixedly connects a top end of a piston rod of the lifting oil cylinder with the small rotary table, the clamp is fixed on the bracket, the guide rail is fixed on a side surface of the large numerical control rotary table, and the guide rail is in sliding connection with the clamp; a positioning cone is arranged on the small rotary table, and a pull pin corresponding to the positioning cone in position is arranged under the small rotary table board; and is configured so that in use the lifting oil cylinder lifts the small rotary table along the guide rail through the bracket, a top surface of the shifting pin makes contact with the driving curved surface, as the small rotary table ascends, the shifting pin pushes the positioning pin head out of the pin hole so that the small rotary table board is separated from the large rotary table board, the pull pin is fixedly connected with the positioning cone, the small rotary table board is fixedly connected to the small rotary table, the small rotary table drives the small rotary table board to work, and the clamp clasps the guide rail to fix the position of the small rotary table.