The rationality of chair back design is an important index of comfort of an office chair. Sitting in a comfortable office chair can Improve work efficiency and prevent disease. Through the existing literature investigation and preliminary experiments, it can be found that the current defects and difficulties in the design of chair back mainly lie in the curve of chair back, which also attracts the researchers’ interests recently. In this paper, we will study the curve of the back of the chair, measure the spine curve of the human body sitting posture with Qualisys, investigate the existing design problems of the back curve of the chair, and finally put forward suggestions and design basis for the back of the chair based on ergonomics.