A waterproof light-emitting diode (LED) bar lamp bulb, including a lamp base and a shell connected with the lamp base, and further including a stem assembly; the stem assembly is connected to an opening portion of the shell; the stem assembly includes a rubber seat, and a first metal wire, an LED bar, and a second metal wire which are electrically connected with each other in sequence; the rubber seat is matched with the opening portion of the shell; a filling recess is formed by the rubber seat and the opening portion of the shell; and a sealant layer for sealing and waterproofing is arranged at the filling recess.