For the fatigue problem of transmission tower cross arms caused by the wind induced vibration, an experimental study on high cycle(500 thousand times) fatigue performance of a new type GFRP composite material cross arm was carried out. Stress state of these specimens was monitored. The variety of load displacement time curve and the energy dissipation capacity were analyzed. Ultimate bearing capacity of the specimens without significant fatigue failure was evaluated to derive residual bearing capacity. Based on the residual strength theory, the cumulative damage was evaluated and was predicted. It is shown that the GFRP composite material cross arms demonstrate high level of safety redundancy on anti fatigue performance, and the average fatigue life is as high as 55million times under the most adverse loading condition.