An LED lamp includes a housing defining an opening, an LED module received in the housing, a light-guiding cover covering the LED module and a transparent plate hermetically coupled to the housing via glue. The housing includes a main body, a pair of lateral plates secured to two opposite ends thereof and a pair of cushioning plates tightly sandwiched between the lateral plates and the two opposite ends of the main body. Each cushioning plate defines a recessed side edge, whereby two opposite end edges of the transparent plate, the recessed side edges and tops of the lateral plates cooperatively define a pair of receiving grooves at the two opposite ends of the main body of the housing. An outer edge of the transparent plate is hermetically coupled to the housing via glue filled in the receiving grooves.