The invention discloses a servo indexing closed-loop control system on a notching machine, and the system comprises an indexing box body of the notching machine, wherein a servo motor is installed on the indexing box body. The servo indexing closed-loop control system is characterized in that an indexing spindle is installed on the indexing box body of the notching machine, a high-accuracy rotary encoder is installed at the lower end of the indexing spindle, a centring head is fixedly installed at the upper end of the indexing spindle, and a motor stator or a rotor iron chip is installed on the centring head; and the indexing spindle is driven by the servo motor via a mechanical transmission device. The servo indexing closed-loop control system disclosed by the invention is compact in structure, high in control accuracy due to the adoption of servo indexing closed-loop control, high in indexing accuracy, and convenient in operation.