Telescopic rotary chair back assembly and chair thereof

The invention belongs to office furniture, and discloses a telescopic rotary chair back assembly and a chair thereof, the telescopic rotary chair back assembly comprises a back support, an upper backrest, a lower backrest and a telescopic arm, the upper backrest is arranged on the back support, the rear end of the telescopic arm is rotatably connected with the back support, the front end of the telescopic arm is rotatably connected with the lower backrest, and the lower backrest is located at the lower end of the upper backrest; and the telescopic arm telescopically adjusts the distance between the lower backrest and the back bracket. The lower backrest can rotate and stretch out and draw back, self-adaptive adjustment can be carried out according to the waist point of a user, the waist is not prone to running, and the comfort level of the user is improved. 本发明属于办公家具，公开了一种伸缩旋转椅背总成及其座椅，包括背支架、上靠背、下靠背和伸缩臂，所述上靠背设置于背支架上，所述伸缩臂后端与背支架转动连接，前端与下靠背转动连接，下靠背位于上靠背下端，伸缩臂通过伸缩调节下靠背与背支架的距离。本发明的下靠背能够进行旋转和伸缩，可以随着用户的腰点进行自适应调整，不容易