The paper reports the impact of the conditions of mechanical activation for the preparation of ultra-fine coal powders with an increased content of humic acids (HA). With an optimum grinding time of 20min and revolution amplitude of 400, a double increase of HA contents can be achieved. In the process of activated coal grinding insignificant specific surface area (SA) changes occurs due to the increased HA contents. Distribution curves of the active powder culminate at 22nm and with an agglomerated coal sample at 35nm. The aggregation of grains influences the surface properties of the coal powders.