Based on stability theorems for nonlinear differential systems with commensurate fractional orders and on the use of a nonlinear coupling that does not require the total elimination of the nonlinear part of the system, we have obtained an analytical result to ensure the practical and exact synchronization of complex networks with fractional nonlinear order systems as elements. As an application, we present the synchronization with different kinds of fractional differential systems. We use some numerical results to verify the effectiveness of the proposed method.