Conventional theoretical and numerical studies on photonic crystal, which often does not consider the film thickness error during the experimental preparation process, will meet a large deviation between the experiment and the simulation. The filtering characteristics of one-dimensional (1D) photonic crystals with random film thickness errors (modeled as the Gaussian distribution) are systematically investigated by statistical method and numerical simulations. By studying the influence of the deviation of film thickness and the period number on the filter characteristics, it shows that the forbidden bandwidth is reduced to 80.27% of the intrinsic energy band when the film thickness deviation is σ = 0.25 a . Furthermore, we found that introduction of a slight disturbance of the film thickness ( σ = 0.01 a ) to photonic crystal will broaden the forbidden bandwidth to 100.49%. The proposed photonic crystal model with film thickness deviation can reduce the error between experiment and theory, which can be used for designing broadband photonic bandgaps. These structures have potential applications such as light–matter interactions, ultra-small filters, and photonic chips.