A system and method for correcting a nacelle wind velocity of a wind power generator are provided. The nacelle wind velocity correction system includes: a measurement information collection unit that collects a nacelle wind velocity that is measured by a nacelle anemometer that is installed on a nacelle of the wind power generator; a wind velocity difference generator that generates nonlinear wind velocity difference information of a nacelle wind velocity on a unit basis by calculating a wind velocity difference between a standard wind velocity of a met tower that is measured for a predetermined period and the nacelle wind velocity; a correction unit that generates a nonlinear correction equation using the nacelle wind velocity and the nonlinear wind velocity difference information and that calculates a nacelle correction wind velocity according to the nonlinear correction equation; and a controller that controls an operating state of the wind power generator according to a preset cut-in speed and cut-out speed using the nacelle wind velocity.