Determination of municipal wastes (raw compost from a "Dano" system compost processing line) moistness influence on organic matter transformation and elemental composition of humic acids at various compost maturity stages was the study objective. The composting was carried out over a period of 188 days in the following conditions: variant A - composting on a prism with a 50% weight humidity (w/w) at the aeration day (with fluctuations of 44.0-52.0%); variant B – composting in an open-work container (1000 l) with a 50% w/w at the aeration day (with fluctuations of 46.2-53.4%); variant C - composting in an open-work container (1000 l) with a humidity o f 60% w/w (with fluctuations of 46.9-60%). The study showed that higher moistness of composting municipal wastes (variant C) limited mineralization and humification of organic matter and did not provide the sanitary safety of composts. The organic matter transformation in such a moistness conditions led to formation of the specific humic compounds with an excess of the humic acids over the fulvic acids. However the particles of humic acids indicated low level of aromatization and possessed considerable amount of weakly oxidized peripheral groups. The raw compost fast transformation from municipal wastes into the mature product was most favored by the conditions of composting on a prism with a 50% weight humidity (w/w), providing better oxygen access.