Silica nanoparticles are prominent in the scientific research, as they are easy to synthesize and widely used in various fields, such as catalysis, adsorption (including adsorption of pigments), medicine, manufacturing of electronic and thin supports, and electronic insulation materials. The quality of most of these products is largely dependent on the size and size distribution of the particles and the nature, content, and stability of their functional groups. The formation of silica nanoparticles and their size are controlled by the rate of two reactions: alkoxysilanes hydrolysis to form oligomers with silanol groups and condensation of oligomers to form siloxane bonds. In the 1968 year Stober described the synthesis of monodisperse spherical silica nanoparticles by hydrolytic polycondensation of silicon alkoxides in aqueous alcohol solutions in the presence of ammonia [1]. So, there were synthesized silica particles ranging in size from 50 nm to 1.5 microns with narrow size distribution. In the same publication, it was shown that with increasing concentration of ammonia, the size of silica particles decreases. With respect to the concentration of water and alcohol, it was necessary to select specific conditions. Later [2] there was determined the effect of temperature on the particle size. In the 1990s [3] there were initiated research on the fictionalization of silica particles, which significantly extended the range of their application. There were suggested two main approaches: surface modification of ready-made silica particles or one-step fictionalization during synthesis by introducing trifunctional silanes. The authors of this paper considered further obtaining particles with 3-aminopropyl functional groups [4]. It was determined that the addition of 3-aminopropyltriethoxysilane (APTES) to ethanol-ammonia solution containing already formed silica particles did not lead to the consolidation of amino groups on their surface. That required boiling or changing the sequence of alkoxysilanes addition (first APTES, then tetraethoxysilane (TEOS)). However, there was not conducted a systematic analysis of the impact of factors in such systems. Therefore, using the two-component system TEOS/APTES, the effect of various factors, such as the order of components addition, stirring time, drying mode, reacting alkoxysilanes ratio, temperature, concentration of water and solvent, on the morphology of silica spheres and the content of functional groups was studied. It was shown that the shape and size of the particles (100-700 nm) were significantly influenced by the synthesis temperature; and the content of 3-aminopropyl groups (3 mmol/g) depended on the reacting alkoxysilanes ratio. Thus, using the determined relationships, synthesis of silica spheres functionalized with amino groups can be conducted.