Here　we　report　the　contribution　of　self-absorption　to　excitonic　luminescence　in　an　ultrathin-walled　ZnO　semiconductor　microtube　cavity.　The　trapping　structure　regulates　the　X-band　and　near-band　edge　emission　via　various　excitation-detection　geometries.　The　self-absorption　in　the　microcavity　results　in　a　high　concentration　of　exciton　similar　to　3.65　x　10(16)　cm(-3)　and　boosts　the　amplified　spontaneous　emission.　The　enhancement　ratio　for　the　UV　band　emissions　can　be　up　to　40　folds,　higher　than　using　localized　surface　plasmon　resonance　via　Ag　nanoparticles.　The　coefficient　of　self-absorption　by　the　light-trapping　microtube　structure　is　therefore　determined　to　be　6.1.　The　present　work　opens　up　new　opportunities　to　enhance　the　photons　collection　and　interaction　with　excitons　in　wide-band-gap　semiconductor　for　on-chip　wavelength-tunable　UV-luminescence　devices　in　optoelectronic　applications.