A watertight rope light of the present invention includes two parallel wires, a plurality of light emitting diodes and a transparent enclosing layer. The light emitting diodes are substantially parallel to the wires. Each light emitting diode has a semiconductor die, a lens, an anode leg and a cathode leg. The lens has a distal end, which is formed with an awl-shaped concave surface, and the semiconductor die is adapted to emit light toward the concave surface. As such, the light emitted from the semiconductor die can be reflected radially outward to illuminate the surrounding uniformly.