The invention provides a solar street lamp which comprises a hollow lamp post, a lamp arm, a lamp bulb, a solar component, a horizontal box and a box cover, wherein the lamp arm is arranged on one side of the lamp post, the lamp bulb is mounted on the lamp arm, the solar component can supply power for the lamp bulb, and the box cover is arrange don the box. A first connecting hole is formed in thebottom wall of the box in a penetrating manner, a second connecting hole directly facing the first connecting hole is formed in the box cover in a penetrating manner, the upper end of the lamp post sequentially penetrates the first connecting hole and the second connecting hole, the lamp post is hermetically and fixedly connected with the box, the box cover is vertically provided with a pluralityof water inlet micro-holes, a water drainage hole is formed in the side wall of the lamp post, a box inner cavity is communicated with a lamp post inner cavity through the water drainage hole, and awater outlet is formed in the side wall of the lower end of the lamp post in a penetrating manner, the lamp post inner cavity is communicated with the outside through the water outlet, a gas inlet isformed in the upper side wall of the lamp post in a penetrating manner, a fan is mounted at the gas inlet, gas can be led into the lamp post by the fan, the solar component supplies power for the fan,and a controller for controlling opening and closing of the water outlet is arranged on the lamp post. The solar street lamp is stable in working.