Abstract: A multi-ribbed composite wall is the main bearing member of a new structural systemmulti-ribbed slab structure. According to the results of previous studying, the elastic simplified mathematical model of the multi-ribbed composite wall is studied. Based on the experimental research on the frame grid elements of the wall. It is discussed the influence of the main factors on the mechanical behaviors and failure modes of the frame grid elements, such as the rigidity of beams and columns in frames, the mechanical properties of filling materials and others. The oblique compression bar which diagonally articulates with reinforced concrete frame is adopted to simulate the action of filler block on the whole wall, and that the width formula of the equivalent oblique compression bar is obtained by analyzing and constructing. On this basis the rigid frame-oblique compression bar. s simplified mathematical model which is suitable for the multi-ribbed composite wall is established. Furthermore the elastic lateral stiffness formula of the rigid frame-oblique compression bar is deduced. Theoretical analysis shows that the rigid frame-oblique compression bar can better reflect the real mechanical behavior of the multi-ribbed composite wall and is a kind of reasonable simplified mathematical model.