The lumbar support assistive device includes a plastic rigid main member having a half-fusiform whose front side curves in accordance with human spine. A trough is provided along the front side extended in an axial direction to a bottom side of the main member. A number of forward bulging semi-ellipsoidal elements are arranged at intervals in two columns along lateral sides of the trough. The semi-ellipsoidal elements closer to a bottom of the main member are wider and higher； and the semi-ellipsoidal elements closer to a top of the main member are narrower and lower, and they are closer to the semi-ellipsoidal elements in the other column These semi-ellipsoidal elements provide massaging effect and support to corresponding intervertebral discs of the spine. The semi-ellipsoidal elements also raise the lumbar support assistive device to provide enhanced ventilation so that wearing the lumbar support assistive device would not feel sultry.
