With the increasing demands for new biological extinction materials in military and civilian fields, the artificially prepared flocculent particles were equivalent to bullet rosette particles, which were further used to build the biological particles with different structures as a unit particle. And the structures of biological particles were characterized by parameterization. Then the discrete dipole approximation (DDA) method was used to calculate the average extinction efficiency factor for biological particles in the far infrared band. The results indicate that the average extinction efficiency factor of biological particles is positively correlated to the size factor and porosity in the far infrared band. Based on studying the relationship of average extinction efficiency factor with size factor and porosity, the biological particles average extinction efficiency factor model in the far infrared band was constructed. Using that model, the computation time was shorter than that of the DDA method, and the calculation error is less than 10%. The model provides a theoretical basis for the further development and morphology control of biological extinction materials.