The aim of the research is to study the effectiveness of complex humatised mineral fertilizers (CHMF) on fertile quali- ties of gray soil. The problems were to study the influence of CHMF on fertile qualities of gray soil, basing on field experi- ments, as well as to study the optimal ratio of constituent parts of CHMF. The objects of the research were CHMF in their structure containing GMUK (including ammonium nitrate, sodium humate and trace elements, as well as glauconite- potassium component) and phosphoric component (phosphorites), as well as gray soils. The research methods included field experiments, soil sampling, determination of qualitative characteristics of the soil (humus, labile phospho- rus and exchange potassium). Investigated soils were medi- um loamy gray soils of old irrigation. It was established that the using CHMF would lead to the increase humus content in the soil, labile phosphorus and exchange potassium. After using CHMF, relatively to their initial values in the soil (before using CHMF), the soil content was: humus - from 178.6 to201.9 %, labile phosphorus - from 172.7 to 293.2 % and ex- change potassium - from 114.0 to 120,0 %. At the end of vegetative season, due to using nutrients by cotton from the soil, their content in the soil decreased. At the end of vegeta- tive season, relatively to their initial values in the soil (before the use of CHMF), the content of the soil was: humus - fromto 144.0 %, labile phosphorus - from 100 to 167.8 % and exchange potassium - from 94.1 to 101.6 %. Thus, using CHMF as a fertilizer, despite the decrease in the nutrients at the end of vegetative season, the content of humus, labile phosphorus and exchange potassium in the soil was equiva- lent or would exceed their values in the soil prior to fertiliza-tion. It was found out that the most optimal composition of CHMF was the ratio: GMUK - 70 % and phosphorites - 30 %.