Currently, a major problem in the Republic of Moldova is the low soil fertility, as a consequence of its uncontrolled exploitation. To solve this problem were carried several works to increase the degree of soil fertility, among which the composting method is known from ancient times. Biohumus proceeded from cattle manure is the best natural fertilizer, which can be easely produced in any animal farm, rich in nutritious substances for plants, compared with artificial fertilizers. In experimental production, the cattle manure were subjected to traditional composting in especially arranged for this purpose places on the farm of TES “Maximovca”. Samples of unfermented and partially fermented manure after 2, 4, 6 months were investigated microbiologically using selective nutrient media, produced by HiMedia, India, for determining the total quantity of microorganisms of the species Bacillus, E. coli, Pseudomonas aeruginosa, Klebsiela pneumoniae and fungi. In the initial unfermented manure were found 5,0x108 m.c./g of bacteria, including 1,1x108 m.c./g Bacillus spp., 2,4x106 m.c./g E. coli and 7,0x109 m.c./g fungi, including 9,0x106 m.c./g Candida species. During 2 months of fermentation of manure, a total decrease of the quantity of microorganisms from 5,0x108 m.c./g to 5,0x107 m.c./g took place, this amount was maintained up to 4 months of fermentation. The intensification of the fermentative activity of microorganisms Bacillus was detected after 2 months of fermentation of manure by the quantitative increase of species B. subtilis up to 8,0x1010 m.c./g and B. megaterium up to 6,0x1011 m.c./g. In the partially fermented manure during 4 and 6 months, their quantity were kept in the limit 1,3–7,0x106 m.c./g. It is known that the ammonifying bacteria B. subtilis and B. megaterium through their activity contribute to the transformation of nutritive substrate in accessible for plants forms. In our research, Ps. aeruginosa was detected only at the initial stage in an amount of 8,0x107 m.c./g, which does not confirm the recent publications confirming that this agent is the most widespread microorganism in the composting process. Klebsiela pneumoniae is a microorganism resistant to the environmental conditions due to its capsule. In our study, the maximum amount of this agent was found in the fermented manure during 2 months and was not detected in the final product. In the obtained biohumus, after 6 months of traditional fermentation, the total number of microorganisms increased, the amount of fungi decreased till 5,0x106 m.c./g and the species of genus Candida – from 9,0x106 m.c./g till 6,0x102 m.c./g . Thus, in the biohumus obtained during the 6 months of traditional fermentation of cattle manure (containing gastrointestinal microflora), the amount of Bacillus bacteria exceeds 50% of the total number of microorganisms, which in the process of the competitive interaction leads to the elimination of the conditionally pathogenic microflora (Ps. aeruginosa, Kl. pneumoniae, Candida species), to decrease of the ammonia nitrogen amount and increase of the total nitrogen amount more than 2 times. These data can be used, in the future, in the control of the parameters of biohumus formation.