The present invention provides a U-shaped luminaire, comprises a lamp head module, a first glass tube, a second glass tube, a first light source board, a second light source board and a light transmission module, said lamp head module engaging said first glass tube and said second glass tube respectively, said first light source board being located within said first glass tube, said second light source board being located within said second glass tube and said light transmission module engaging said first glass tube and said second glass tube respectively.