When the main dimensions of a generator are fixed, the damper winding performance is the most important factor affecting the subtransient reactance of the generator. According to different situations, the end users have different requirements for subtransient reactance. The adjustment of damper winding could basically meet the requirements of the special subtransient reactance. The subtransient reactance of a 3 MW synchronous generator damper winding with different materials or different bar numbers was calculated. The calculation results were verified by low voltage sudden short circuit testing, and then the optimal damper winding design was obtained.