A lens structure includes a lens barrel, a lens upper cover, a lens lower cover, and a sealing ring. The lens barrel includes a front portion and a rear portion respectively at two opposite ends on an axial direction. The lens barrel has an external annular wall. The lens upper cover is fixed to the front portion. The lens upper cover includes a lower flange and an abutting ring radially protruded from an outer periphery of the lower flange. An inner diameter of the lower flange is greater than an outer diameter of the external annular wall. The lens lower cover forms an annular shape and abuts against the lens upper cover. The lens lower cover is fixed to the lower flange. The lens lower cover, the lower flange, and the abutting ring jointly form an annular slot. The sealing ring is received in the annular slot.