Abstract: Based on the cost-benefit analysis of wind power projects, the concepts of “differential cost per kWh” and “differential cost per kWh in full life cycle” are put forward for the first time, and the formulae are also derived, which facilitates the efficient and optimal selecting of wind turbine generator system(WTGS) under limited information conditions. It is also pointed out that generation capacity coefficient shall not be the only major factor for WTGS selection, while WTGS with lowest differential cost per kWh in full life cycle shall also be chosen. If differential costs per kWh in full life cycle of several types of wind turbines are same or close to each other, then the wind turbine with lower differential cost per kWh or higher generation capacity coefficient shall be selected. Optimal WTGS can capture maximum wind energy, reduce cost per kWh in full life cycle for wind power projects, and achieve maximum economic benefits.