Abstarct: In recent years, with the expansion of civil infrastructure, as well as the lack of areas with suitable geotechnical characteristics for construction, soil improvement has become very important. Problems such as the need to spend high energy in terms of performance, limited depth of improvement and the cost of equipment required in existing methods such as preloading, the use of reinforcements or additives such as lime, cement and other chemicals, Has led researchers to use low-cost methods. Also, pollution in the environment in some improvement methods, including the use of chemicals such as lime and cement has caused some environmental problems such as pollution. The use of some soil improvement methods has also changed the direction of groundwater aquifers, which due to human contact with groundwater can endanger its health. Therefore, it is necessary to use new methods of improvement and environmentally friendly. Microbial geotechnology is a new branch of geotechnical engineering that studies the possibility of improving problematic soils using microbiological methods. Currently, most microbial geotechnical studies are in the laboratory stage and due to its complexity, the application of microbial geotechnology requires interdisciplinary study between microbiological disciplines, environment, geochemistry with geotechnical engineering. In this research, biological improvement of Firoozkooh silicate sandy soils have been performed using Sporosarcina pasteurii bacteria. Using a dynamic simple shear test device, dynamic experiments were performed on soil samples with a height of 4 cm and a diameter of 10 cm at three surcharge of 100, 200 and 300 kPa. As a result of experiments, the shear modulus increases by about 23% at low strains and by about 1% at high strains, the damping decreases slightly, the shear wave velocity increases by about 18 to 20% and the maximum shear modulus by about 35 to 45 percentage and reduction of normalized shear modulus is observed.