An optical module includes a housing, at least one optical assembly and at least one sealing member. The housing includes a housing body, a cover and at least one vent hole therein. At least part of each optical assembly is located in the housing body. Each sealing member is located at a respective one of the at least one vent hole. The sealing member has a central axis and includes a first cylinder, a truncated cone, and a second cylinder, a diameter of the first cylinder is greater than a diameter of the second cylinder. Each vent hole is a stepped hole including a portion with a first aperture and a portion with a second aperture, the first aperture is greater than the second aperture. The first cylinder fits the portion with the first aperture, and the second cylinder fits the portion with the second aperture.