This paper propose a route to decorated end facet of single mode optical fibers with colloidal photonic crystals and present the principle for this structure to be used as relative humidity sensing. The approaches of preparing PS colloidal crystals, composite colloidal crystals, and SiO2 inverse opals on the end faces of optical fibers by vertical deposition was studied. The prepared colloidal crystals and inverse opal were structurally characterized, and the reflection spectra of the photonic crystals-modified microstructure optical fibers was measured. The relative humidity sensing characteristics of composite photonic crystals decorated microstructure optical fibers were tested. Finally, a capillary-fiber structure was proposed to improve the quality and mechanical stability of the colloidal crystals fabricated on the fiber endfaces.