Monodispersed silica nanoparticles were assembled into opaline photonic crystal beads and cemented together by sintering in order to enhance the mechanical stability of the beads, which simulates the formation of nature opal. The sintering temperatures and structures of the sintered beads were investigated. The results showed that by sintering treatment at temperatures between 700 degrees C and 1000 degrees C for 2 hours the beads were more reliable for multiplex bioassay applications in mechanical robustness, fluorescent background, sensitivity and encoding ability. It is anticipated that the opal-like beads have wide applications in multiplex protein and nucleic acid analysis.