We propose a general correction method for the efficiency measurement of optical components in the 45–110 nm range to eliminate the contamination of higher-order harmonics at beamline U27 of the Hefei Light Source (HLS). The influence of harmonics can be deducted effectively from the initial measurement results through the analysis of the proportion of harmonics with a transmission grating and the efficiency measurement of optical elements at the harmonics wavelengths. The reflectivity measurement of a gold film is performed at the beamline to verify its validity. Results indicate that the corrected reflectivity is in good agreement with the theoretical value. The maximal deviation amounts to 1.93% at a wavelength of 85 nm and an incident angle of 5?.