Rhodamine B (RhB) was incorporated into polyethylene glycol diacrylate (PEGDA) and ethoxylated trimethylolpropane triacrylate (ETPTA) to prepare RhB-PEGDA/ETPTA with different photonic band gaps Inverse opal structure photonic crystal composite film. The composite film was characterized by reflection spectrum and fluorescence spectrum. And the fluorescence polarization performance regulation of RhB by photonic crystal was studied. The results show that when the photonic bandgap of the photonic crystal composite film exactly matches its emission peak (595 nm), the polarization state of the emitted light is regulated successfully. When the thickness of the photonic crystal layer is 6.94 μm, the fluorescence polarization regulation effect is the best, and the polarization anisotropy value is 0. When the photonic bandgap of the inverse opal composite film matches the excitation wavelength (555 nm), the polarization anisotropy value is 0.082; when it matches red band edge of the emission peak (665 nm), the polarization anisotropy value is 0.12; When the emission peaks are uncorrelated (730 nm), the polarization anisotropy value is 0.16, similar with that of pure RhB. All these results indicate that photonic crystals with suitable bandgap can regulate the polarization state of fluorescence.