The contamination of nitrate in groundwater has become an ever-increasing environmental problem. To understand the process of nitrate transformation in soil medium, the experiments of adsorption and denitrification were carried out in this paper. The results indicated that nitrate could not be adsorbed by soil particle, but its intermediary in the denitrification pathway, nitrite occurred obvious adsorption in soil. The influence parameters of nitrite adsorption, such as pH value of solution, initial concentration and temperature, were systematically investigated. In addition, microbe action on nitrate and nitrite was also evaluated in this study. Although attenuation of nitrate and nitrite occurred under natural conditions, external carbon source could accelerate the denitrification process. The efficiency of nitrate attenuation was only about 5% by the end of 30 d experimental period. However, the enhanced degradation of nitrate approached 50% within 14 d, with the appearance of nitrite accumulation.