The invention relates to a large-range illumination cross arm street lamp easy to install in the field of power transmission line auxiliary devices. The street lamp comprises a cross arm body, solar cells, super-bright LED lamps and maintenance-free valve control type sealed storage batteries. The crystalline silicone solar cells are arranged on the upper surface of the cross arm body. The two ends of the cross arm body are each provided with one super-bright LED lamp. The side, connected with the cross arm body, of each super-bright LED lamp is internally and fixedly provided with the corresponding the maintenance-free valve control type sealed storage battery through which the corresponding solar cell and the LED lamp are communicated. The street lamp can avoid mutual influences of a cross arm and the street lamp, and therefore large-range illumination of the street lamp is convenient.