Abstract: The biological material has the characteristics of low production cost, wide particle size distribution and no pollution, it can be used as a new type of extinction material. In order to study the atmospheric suspension settling characteristics of biological extinction material FANS 233D, the settling velocity according to the Stokes law and the weighted average algorithm of particle number was calculated. A cluster-cluster aggregation model was used to simulate the fractal structure of the biological aggregated particles while Newton's second law was used to calculate the settling velocity of aggregated particles with different fractal structures. The results indicate that the average settling velocity of the aggregated particles with different original particles increases with the increase of the number of original particles,the settling velocity of aggregated particles with the same number of original particles is related to the porosity and fractal dimension. The study on the atmospheric suspension characteristics of biological extinction material provides a theoretical basis for its practical application.