It is a kind of commonly used sofa in home. This is the kind of sofa sold on the market. The utility model has two supporting points to support the user's lumbar vertebra and thoracic vertebrae, and can obtain the effect of matching the curved surface with the back of the body. The angle between the back of the sofa and the seat surface is critical, and the angle is too large or too small, which will cause the user's abdominal muscles to be strong and fatigue. Similarly, the sofa seat width should not be too large, usually in accordance with standard requirements within 540 millimeters, so that the user's legs can be adjusted to sit posture, rest more comfortable.