Abstract: Due to the structurally orthotropic characteristic of composite concrete two-way slab with precast ribbed panel (composite two-way slab), the look-up table method of isotropic cast-in-place slab could not be directly used. Basic differential equation of deflection surface for composite concrete two-way slab with simply supported edges under uniformly distributed loads was established, the calculation formulae for the deflection and bending moment were obtained. Through the transformation of function form and the introduction of equivalent span ratio, simplified elastic calculation method of composite two-way slab with simply supported edges under uniformly distributed loads was presented. The elasticity coefficients for composite two-way slab with the stiffness ratio of 2 and 0.5 were obtained according to program calculate. The comparison of elasticity coefficients between the simplified elastic calculation method and the look-up table method was conducted, which shows that the simplified elastic calculation method is accurate and feasible.