Abstract: The reflection spectra of Aspergillus niger spores within the waveband of 2.5-15 m were measured by squash method. Based on the measured data, complex refractive index of Aspergillus niger spores within the waveband of 2.5-15 m were calculated by using Krames-Kronig (K-K) relationship. Then, the mass extinction coefficient of Aspergillus niger spores within the waveband of 2.5-15 m were obtained by utilizing Mie scattering theory, and the results were analyzed and discussed. The average mass extinction coefficient of Aspergillus niger spores is 0.68 m2/g in the range of 2.5-15 m, and the average mass extinction coefficient decreases monotonically with the particle size increases. Compared with common inorganic compounds, Aspergillus niger spores possesses a good extinction performance within the waveband of 2.5-15 m, and the requirement of particle size is relative wide in a certain extinction performance.