Highly unbalanced displacement problems arise in low permeability reservoirs during high water cut period caused by interlayer heterogeneity of petrophysical properties. Radial drilling is one of the important technologies to solve this problem. Branch number and branch length are the mainly variables affecting the performance of radial drilling. To achieve equilibrium displacement, an optimization model of the radial drilling branch length and number was established for two-layer comingled production reservoir by considering the inter-layer heterogeneities and displacement, and the corresponding calculation program were developed. Using reservoir numerical simulation technology, the prediction results show that radial drilling can solve the unbalanced displacement problems effectively and also prove the accuracy and applicability of this model.