An LED lamp assembly includes a receiving member, a first LED lamp and a second LED lamp. The receiving member has a pair of opposite slope surfaces. The first and second LED lamps are mounted on the opposite slope surfaces of the receiving member. Each of the first and second LED lamps includes a heat sink and a plurality of LED modules mounted on the heat sink. A number of the LED modules of the first LED lamp is more than that of the second LED lamp. When the LED lamp assembly is mounted on a roadside, the first LED lamp is oriented slantwise toward a leaving direction of vehicles while the second LED is oriented slantwise toward a coming direction of the vehicles.