Fiber reinforced plastics ( FRP ) have the advantages of high strength and good ductility. However,FRP profiles and components have only one-way mechanical properties,transverse strength and stiffness are low, hence the lateral deformation is more prone to buckling. In this paper, the web compression test was carried out on the rectangular cross section polyurethane pultruded section with different width of the support plates.The failure mode of the hollow pultruded profile under the transverse load was the flexion of the flange and the extension of the middle of the web. The width of the support plate was extremely significant for increasing the ultimate bearing capacity of the components. Based on the design formula, the calculation error of pultruded profiles was discussed and analyzed by different calculation formulas.The results show that the calculated results proposed by the paper  is close to the experimental results,and the other formulas are different from the experimental results.