The study results of loading effect when acting a low temperature plasma of oxygen − nitrogen mixtures on the surface of polypropylene (PP) film are resulted. Gravimetric technique for research of etching process kinetics was used. The surface properties of PP were characterized by Fourier Transform Infrared by Attenuated Total Reflectance (FT-IR/ATR). Loading effect was appeared in all range of gas compounds. It accompanied by growth of functional groups content in the modified layer. In the general case loading effect is more expressed if the initial gas contents less of oxygen. A degree of this dependence differs strongly in different intervals of O2:N2 relation owing to extreme kind of changes of active particles flows from plasma in the sample PP. Influence of gas composition on loading effect is relatively small when O2 portion in mixture constitutes 100-10%. Load extent increase results in growth of concentration of oxygen-containing groups, nitrogen-contaning groups were not registered. Interference of heterogeneous and volumetric processes enhances considerably if O2 portion in mixture is lower then 10%. Water vapors enter into a reactions of etching because of the oxygen deficit. Nitriding of the surface occurs along with oxidation of it. Competition of this processes exhibits more strongly when load extent is increased.