Abstract: There are different factors that affect soil microbial biomass, including: soil factors (such as soil physical and chemical properties), soil environmental factors (such as temperature, moisture, pH etc.), and soil management factors (such as use of chemical fertilizers, heavy metals, pesticides, addition of organic matter, cultivation and crop rotation, seasonal variation, tillage, land use etc.). This review is mainly focusing on the pesticides particularly herbicides as a factor affecting the microbial biomass in different soils. The influence of herbicides on microbial biomass in different soils under different conditions has been reviewed. Herbicides have various effects associated with the type of herbicides, the concentration of the herbicides, the type of soils, and the conditions of the experiment (temperature, moisture, and the time of incubation etc.). The significance of these effects has been discussed.