One of the main causes of climate change is greenhouse gases, which are dominated by an increased amount of CO2 in the atmosphere. The agricultural sector is one of the most important sources of greenhouse gas emissions. The goal is to prepare the calculation models-system of "Ūkio ŠESD" at the farm level. When reducing GHG emissions, it is important to accurately determine gas emissions at the farm level, while applying the GHG emissions accounting model, it is aimed to assess emission sources and apply effective measures to reduce gas emissions. According to the IPCC methodology, based on the experience of other countries, a spectrum of GHG emission sources has been determined at the farm level, including criteria defining the sustainability of the farm, and a methodology and system for accounting for GHG emissions at the farm level has been created. The developed model-system for calculating GHG emissions is calculated in three stages. The animal population is divided into subgroups and each of them is described. The emission coefficients of each subgroup in kilograms per animal per year and the number of animals in the subgroup are evaluated. Three (Tier 1, Tier 2, Tier 3) detail and complexity methods were used for calculation. The accounting system for GHG emissions at the farm level is created according to specially prepared GHG calculation methodologies, adapted formulas with selected variables and parameters. The prototype of the created accounting system is intended for use in the accounting of national greenhouse gas emissions and in "green" certification, for providing consulting services. By applying the GHG emissions accounting system, the main aspects of the mixed, livestock and crop farming activities influencing GHG were evaluated. In animal husbandry, the most GHG emission into the environment is CH4 gas, which accounts for as much as 91% of GHG emissions in animal husbandry: 79.0% evaporates from animal digestion processes and 11.6% from manure management systems. Most methane evaporates from the digestive systems of cows (55.6%), from other cattle - 39.2%, and from sheep - 3.0%. In order to determine GHG emissions in animal husbandry, it is necessary to estimate emissions of the following gases: methane (CH4); nitrous oxide (N2O). Methane gas emissions are determined from animal digestion processes and manure management technologies, nitrous oxide - direct and indirect emissions from manure. When calculating or experimentally determining the emission coefficients of methane and nitrous oxide gases, it is necessary to evaluate the conditions of keeping animals, the applied modern manure management technologies (manure removal from the barn, manure pits, manure incorporation into the soil), applied biomeasures to optimize fermentation and microbiological processes, and temperature changes. A methodically based GHG accounting system, which will record more accurate data collection in specific farms, would enable the state to know problem areas to which support measures aimed at reducing GHG emissions could be directed more appropriately, to carry out monitoring and to analyze the benefits provided by the support.