Abstract: A post-filling method was proposed to prepare composite photonic crystals with both stability and good structural color effects. The patterned Poly(styrene-methacrylic acid) (P(St-MAA)) photonic crystal color structure was prepared by adopting the colloidal microsphere self-assembly method, and then the P(St-MAA) photonic crystal was filled with SiO₂ sol. The filling conditions of SiO₂ were optimized, and the structural color effect and stability changes of the photonic crystal color structure before and after filling were compared. The results show that: P(St-MAA) colloidal microspheres with particle diameters of 230 nm, 258 nm and 287 nm can be constructed to obtain photonic crystals with regular arrangement and bright structure, but the stability of the crystal structure is not good; when the concentration of SiO₂ does not exceed 30wt% and the filling time is less than 5 min, the SiO₂-P(St-MAA) composite photonic crystal with bright structure color can be prepared; under the same stability test conditions, the stability of the composite photonic crystal is significantly improved, and the structure color effect is not easy to subtract, which is mainly due to the SiO₂ acting like a “bridge”, strengthening the adhesion of adjacent P(St-MAA) colloidal microspheres, and enhancing the adhesion between the photonic crystal layer and the substrate. This research will provide new ideas for the construction of high-quality photonic crystals, and is expected to promote the practical application of photonic crystal chromogenic structures.