Wind turbine design today has the ability to operate at different rotational speed. Together with the pitch control system of the turbine, its maximum rotational speed is where it is required for safety reason and limit the system’s electrical and mechanical load. A study of structural response under different wind speed using numerical analysis software in order to assess fatigue performance of the steel tower. To understand the relationship between wind speed and tower structural response, structural stress are obtained with different constant wind speed. Analyses are carried out to assess the sensitivity of structural response to wind speed and gain understanding and relevancies of certain inputs in relation to variation of output. Second analysis is done by varying the time step and third analysis is to compare performance between the different software versions.