Abstract: A new type of S355ML steel for offshore wind power was developed by three methods with different carbon content and refined grain element addition. The results show that the microstructure of S355ML steel plate had no obvious change after 7% pre-strain and aging treatment at 250℃ for 1 h. The strain aging sensitivity of S355ML steel developed by reducing carbon content and adding more refined grain elements was low, and its mechanical properties fully met the needs of engineering projects, and the cost of this method was the lowest.