Biological soil stabilization is a new and environment friendly method of soil improvement. In this method the urease activity of a bacteria cause the precipitation of the calcium carbonate in the soil medium. This method has been performed by injection of solutions to the soil which are contained the needed materials for initiating the process. Besides the soil properties such as soil grading, porosity, etc., the cementation solution properties affects the obtained results of this method. The latter properties include injection method, solution concentration and pH. As a result, this process causes the bounding of the soil grains. Another important result of the mentioned method is decreasing the permeability of the soil. This research presents the results of permeability tests on soils treated with microorganism. An engineering landfill liner model also is developed to evaluate the effect of the biological soil improvement method on controlling the leakage of the waste liquids from the landfill into the surrounding grounds