The invention relates to a caution board mounting bracket used in a power line tower, which comprises a glass fiber reinforced plastic brand body mounting bracket, a glass fiber reinforced plastic fixed ear-frame which is arranged on the glass fiber reinforced plastic brand body mounting bracket, and a glass fiber reinforced plastic fixed pressing frame which is used for fixing side bar angle steel and is matched with the glass fiber reinforced plastic fixed ear-frame. The cross sections of the profiles of the glass fiber reinforced plastic brand body mounting bracket, the glass fiber reinforced plastic fixed ear-frame and the glass fiber reinforced plastic fixed pressing frame which form the invention are a rectangle, a round or an ellipse; and the cross sections of the profiles of the glass fiber reinforced plastic brand body mounting bracket, the glass fiber reinforced plastic fixed ear-frame and the glass fiber reinforced plastic fixed pressing frame which form the invention are in a 'T' shape, an inverse 'L' shape or an 'I' shape. The caution board mounting bracket of the invention has the advantages of good tensile strength and anti-kink performance, corrosion resistance, and no stealing and selling value, thus being suitable for long-term use under unattended condition in the fields.