There is provided a luminance correction system for an organic light emitting display, in which reference offset values are set in order to correct gamma voltages of reference gray scale levels and an additional offset value is set for at least one gray scale level among the remaining gray scale levels other than the reference gray scale levels to apply the offset value to the correction of the gamma voltage corresponding to the gray scale level so as to prevent color coordinates from being distorted in the respective gray scale levels and luminance components.