A micromechanical model is constructed for the elastic modulus of nano-fibrous scaffold. The nano-fibrous scaffold was obtained using electrospinning method with polymeric materials, and was supposed to be created with linear elastic strain rods that are straight in the range of rod length. Statistical theory was introduced to model the random distribution of fiber segment length and the percolation effect was also studied. Model predictions were verified using experimental data. This model can be used to study the relationship between the elastic modulus of the scaffold with respect to the fiber concentration, fiber diameter and fiber orientation.