In this paper, we study the global robust synchronization problem of the controlled Duffing system and the Van der Pol oscillator. By employing the internal model approach, we first show that the problem can be converted into a global robust stabilization problem of a time-varying nonlinear system in lower triangular form. Then we show that the global stabilization problem of the lower triangular system is solvable, thus leading to the solution of the global robust synchronization problem.