A lens tube and a mounting base thereof comprise a lens tube for reception of a lens array and a mounting base for accommodation of an image sensor. On an outer periphery of the lens tube is formed a first conical surface, and in the mounting base is formed a concave portion. A second conical surface is formed in the concave portion for mating with the first conical surface of the lens tube. The first conical surface of the lens tube and the second conical surface of the mounting base can cooperate with each other, so as to prevent dust contamination and to make the central axis aligned with the optical axis.