A series of three point bending tests have been conducted on eleven U section GFRP paulownia wood sandwich composite specimens. Through the experiment studies, bending failure modes, load strain curves and the characteristic of strain distribution of the U section sandwich plates were achieved. The influences of the layers of GFRP, paulownia wood thickness and span depth ratio on the behavior of specimens were discussed. The test results show that the carrying capacities of specimens will increase as the layers of GFRP or the thickness of paulownia wood increases. For the specimens with thicker paulownia wood, increase of layers of GFRP can enhance the carrying capacity of specimens more obviously. When the layers of GFRP increase from 4 to 6 and 8, the carrying capacity of specimens of the paulownia wood (height 35mm) increases by 3370% and 6659% respectively. When the span depth ratio increases from 8 to 18, the stiffness of sepcimens with 4 and 6 layers of GFRP decreases by 8194% and 7888%, and the carrying capacity decreases by 52.00% and 3816% respectively. Comparison with GFRP sheet piles shows that U section GFRP paulownia wood sandwich composite plates have an increase of stiffness from 2924% to 18197%.