A knotted and interconnected skeleton structural (KISS) model is proposed for predicting Young's modulus of polymer blends. The KISS model accounts for the structure variations of polymer blends using the percolation theory and emphasizes the structural symmetry of co-continuous polymer blends. It reduces to the Maxwell-Eucken models below the percolation threshold and a symmetric interconnected skeleton structure at an intermediate component volume fraction. The KISS model satisfactorily predicts the Young's modulus of polymer blends for the entire component volume fraction range. Due to mathematical analogy, the model might equally be applied to predictions of electrical and thermal conductivity of binary mixtures.