Topological properties of one-dimensional periodic systems are characterized by the Zak phase, which is essential for describing protected edge or surface states that are robust against disorder and perturbations. Here, we explicitly calculate the Zak phases of a one-dimensional topological photonic crystal with guided-mode resonance using the Finite-Difference Time-Domain method. The retrieved time-dependent Zak phases are found to be zero for trivial and π for nontrivial photonic crystals respectively, which ensures the bulk-edge correspondence, even in a non-Hermitian condition.