Effect of application of NH₄⁺ and glucose on dynamics of three kinds of amino sugars (glucosamine, galactosamine and muramic acid) in mollisol was investigated through laboratory incubation. Relative contribution of microbial communities to nutrient immobilization was explored in relation to the ratio of glucosamine and muramic acid. Results show that contents of the soil amino sugars were influenced evidently to a various extent by the extraneous glucose and NH₄⁺. Concentration of muramic acid was significantly affected by the substrate added, regulating and balancing supply and demand of carbon or nitrogen to a certain extent. Glucosamine was more stable than muramic acid and subject to decomposition in the case of extreme carbon deficiency. No significant effect of soil nutrient status on galactosamine was observed. Carbon application was important to improve nitrogen fixation by soil microbes. In the presence of activated carbon sources, relatively rich nitrogen supply benefited rapid growth of bacteria, while relatively sufficient carbon sources did fast propagation of fungi.