One of the important tools that have been used to study the rates of nutrient transformations in the soil is the isotopic dilution method to determine the gross rates of release into, or removal from, a mineral nutrient pool. Since Kirkham and Bartholomew first proposed the equations based on the use of tracer data to measure the nutrient transformations in the soil in the 1950’s, several more accurately analytical and numerical solutions have been widely used with the development of analytical technique. The simulation of nitrogen transformation is close to the actual processes, which makes it possible to determine gross nitrogen transformation rates and to deeply study the nitrogen cycling in the soil. However, there are still several uncertain factors in 15N isotopic pool dilution technique, such as uniform distribution of 15N. The principle and estimated methods are introduced to calculate the gross nitrogen transformation rates using 15N isotopic pool dilution and to promote further the research of gross nitrogen transformation.