A street lamp includes a lamp post and a lamp housing mounted on a distal end of the lamp post. An alternating current cable is received in the lamp post. A light source is received in the lamp housing. A power supplying device is electrically connected to the light source via a connecting cable. A connection device includes an Edison screw socket and an Edison male screw plug being detachably and threadedly engaged in the Edison screw socket. The Edison screw socket is electrically coupled to the alternating current cable, and the Edison male screw plug is electrically and mechanically coupled to the power supplying device. The power supplying device is configured for converting an alternating current into direct current and supplying the direct current to the light source.