The present invention relates to the field of network communications and discloses a method for calculating a nonlinear transmission impairment, including: determining that no pump channel exists in an optical fiber link, obtaining a factor of intra-band nonlinear noise that does not pass through an optical filter, and obtaining integral power in signal light bandwidth of a span; correcting the factor of intra-band nonlinear noise that does not pass through an optical filter, to obtain a factor of intra-band nonlinear noise of the span that passes through an optical filter; calculating nonlinear noise of the span; and obtaining total nonlinear noise of the optical fiber link according to the nonlinear noise of the span, and obtaining a nonlinear transmission impairment of the optical fiber link. Embodiments of the present invention further provide an apparatus for calculating a nonlinear transmission impairment of an optical fiber link.