The bend-twist coupling design method of spar cap of 1.5MW wind turbine blade made by biased hybrid fibers is discussed, and the coupling parameter is established. It is found that flap-twist coupling effect is only related to the laminated materials, not sensitive to the geometry shape. When varying the angle of off-axis carbon fibers from 7.5° to 30° and the volume fraction from 10% to 90%, different bend-twist coupling effect can be obtained. The results show that the optimal angle of spar cap is closer to 18°, and of skins are about 13°. When constraints, such as fibers strain, the in-plane shear stress and Von Mises stress of static index, are added on the blade, the spar cap is optimized with about 45% carbon fiber volume fraction and 18° off-axis angle. Finally, the impact of natural frequencies of dynamic performance on the blade design is proved to be inessential.