Moscow is a large metropolis in which the air is affected by the constant effects of chemicals produced by industrial facilities, vehicles, residential heating and other human activities on a daily basis. The protected and park areas on the territory of Moscow have an important recreational role, therefore, air quality control in these territories should be carried out first. Active moss biomonitoring has been used as an alternative method to conventional atmospheric monitoring for more than 40 years. This type of biomonitoring is successfully applied all over the world: in China, Serbia, Moldova, Azerbaijan, Italy, Romania, etc. In this study, active moss biomonitoring was used for the first time on the territory of the Tsaritsyno Museum-Reserve to assess the air pollution. The moss species Sphagnum girgensohnii was chosen for the experiment. Neutron activation analysis was used to determine the concentrations of the elements: Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, Se, As, Br, Rb, Mo, Sr , Sb, Ba, Cs, La, Sm, Tb, Ce, Hf, Ta, W, Th, and U. The concentrations of Pb, Cu, and Cd were determined by atomic absorption spectrometry.