Abstract: The spectral reflectance of biological material FANS 233D in the band of 2.5-15 m was recorded by using infrared microscopic spectrometer. Based on Kramersd-Kronig(K-K) relationship, the complex refractive index of the material in 8-14 m was calculated. A cluster-cluster model was used to stimulate the spatial structure of FANS 233D biological aggregated particles with different fractal dimensions. The extinction parameters of biological aggregated particles with fractal dimension in the far infrared band were calculated by discrete dipole approximation and the mass extinction coefficient was calculated under different conditions. The results indicate that the larger the fractal dimension of biological aggregated particles with the same original particle, the better the extinction performance in the far infrared band. When the value of original particle number, fractal dimension, mass density was 50, 2.00, 1 120 kg/m3 respectively, the mass extinction coefficient in the 8-14 m band can reach 2.262 m2/g. The mass extinction coefficient of the aggregated particles increases slowly with the increase of the original particle radius.