A micro-channel has become a popular scheme in high heat flux electronics cooling. But boiling flow instabilities can occur in these cooling systems with micro-channel heat sinks. These pressure-drop oscillations are limit cycles. We model the system by a van der Pol equation with a control input, which is represented by a control system with a nonlinear feedback element. Using a describing function, we approximate the pressure-drop oscillation in the boiling micro-channel system controlled by a reset controller. Then we obtain a control parameter region where the pressure-drop oscillation is eliminated by the controller. By simulation, we also show that the pressure-drop oscillation is eliminated by the reset controller.