Theultra-compactbiosensorbasedonthetwo-dimensional(2D)photoniccrystal(PhC)microcavityisinvestigated.TheperformancesofthesensorareanalyzedtheoreticallyusingtheFabry-Perot(F-P)cavitymodelandsimulatedusingthefinite-differencetime-domain(FDTD)method.Thesimulationresultsgoalongwiththetheoreticalanalysis.