From an economic point of view, in the process of stabilization of sewage sludge it is important to know the kinetics of decomposition of organic matter and sediment retention time in the stability chamber. This involves, among other things, the investment costs of building installations, expenses related to the operation of technologies or the acreage of the occupied space. One method of stabilization is autothermal thermophilic aerobic digestion (ATAD). The speed of the process of ATAD can be illustrated by examining the individual parameters such as: dry organic matter or chemical demand for oxygen. It was assumed that the ATAD process proceeds in accordance with the law of mass action, which allows for mathematical recognition of completeness of reaction and reaction rate. As a part of its analysis the results obtained on the real object have been referred to the rate equations of various orders. The study was conducted on the sewage sludge derived from a sewage treatment plant in Olecko, where two-step process autothermal aerobic of sewage sludge digestion were introduced. The analysis of the kinetics of stabilization process by substitution of the investigated parameters to the equations illustrating the reactions of consecutive orders, and application of linear approximation. Thus, it has been studied which model of equations are the closest to real values. Moreover, the efficacy of the ATAD process was demonstrated (e.g., by indicating the sludge stabilization). The work to identify the kinetics of the process are aimed at, among others, creating a model describing the speed of the process, including obtaining an answer whether the above equations can be the basis for further work on identifying the factors influencing the stabilization process.