With the increasing penetration rate of renewable energies, the grid-tied inverter usually needs to adapt to complex grid conditions such as large grid impedance, grid voltage fluctuations or even grid faults. However, the grid-tied inverter with phase-locked loop is a nonlinear system. Traditional linear analysis tools are hard to explain large-signal stability problems. Therefore, this study will focus on the modeling and stability analysis of grid-tied inverters considering the phase-locked loop nonlinearity. Using the large-signal reduced-order model, the nonlinear stability analysis is carried out using the phase portrait and Lyapunov’s theorem. On this basis, the parameter optimization method of phase-locked loop is proposed for high robustness with the help of domain of attraction. The above analysis is verified in a three-phase grid-tied inverter prototype simulation.