An LED road light has a heat sink embedded with an LED module, a base and a light pole holder assembly. The base, the heat sink and the light pole holder assembly are assembled by slidably and respectively mounting ribs into slots. Accordingly, the contact area of such engagement is relatively larger than that using screws, thereby enhancing combined strength and extending the life duration of the LED road light. Besides, the engagement mechanism using ribs and slots also provide workers a convenient and time-saving assembling process.