Soil microbial ecology is the study of microorganisms within the soil environment. This chapter describes how microorganisms behave in their soil environment and their role in the soil ecosystem. Soil organisms play crucial and often complementary roles in nutrient cycling, but the complexity of soil structure and dynamic environmental conditions combine to make it difficult for soil microorganisms to achieve their full metabolic potential. Organismal interactions circumvent some of these obstacles and help to maintain soil health and promote the degradation of hazardous wastes. Some interactions between soil microorganisms benefit one or both of the participating populations, whereas other interactions have a negative impact on one of the participants. Clearly, soil contains an enormous diversity of microbial populations, yet we remain woefully ignorant of the forces that control microbiome composition. It’s says that, There is more life below the surface of soil than above. In a single table spoon, there are 50 billion microbes alone. Microbial world in soil is different and microbes play an important role decompose various nutrient and recycling of many nutrients in soil. They are very helpful for growth of the plant and microbes enrich soil is always fertile. So there is need to understand microbial ecology in the soil. In this article we are going to discuss, what is ecology, what is microbial ecology in soil, different type of microorganisms and their interaction and ways to increase microbial population in soil.