Thermomagnetic treatment increases mechanical strength of glass by 20-40 %, microhardness and thermostability by 10-15 %. To control the process of thermomagnetic treatment it is necessary to know the mechanism of interaction of magnetic fields with inorganic glass [1-2]. The aim of the undertaken experiments was to reveal structural changes in flat glass, exposed to constant magnetic field, using section etching by HF solution. Experimental procedures are the following. The samples of flat glass are subjected to the influence of constant magnetic field in laboratory conditions. The main regimes of the thermomagnetic treatment of glass were the following: temperature – between 300 and 600 0С, value of vector’s magnitude of the magnetic induction – up to 160 mT, duration – between 1 and 600 s.     The analyses of glass surface layers were carried out with the help of section etching by HF solution. Three glass samples were fixed in fluorocarbon polymer cassettes and then were joined to the polymer wheel and put into a weak HF solution. The samples rotated in the solution with speed   100 rotations per minute. After etching, the samples were washed with distilled water, dried and weighed. Duration of etching changed within 2.5 to 60 minutes. The temperature of the HF solution made up (30±0.1) oC. Thickness of the dissolved layer and rate of dissolution in HF solution of glass surface layers were calculated based on mass losses of the sample before and after etching. During one etching a layer of glass with thickness from 0.05 up to 1.5 m is dissolved. The relative error of the experiment did not exceed ±4 %. The dissolution of surface layer with the necessary thickness was achieved through different time of etching and changes of hydrodynamics conditions (the samples were rotated in solution or kept in stationary position). The analysis of samples was carried out at the depth 20 µm. Concentrations of Na+, K+ and Ca2+ were measured in extracts after etching using the method of flame photometry. In the following experiments samples were kept in solution in stationary position, i. e. without rotation. Section etching was supplemented by light microscopy and determination of microhardness. The samples were viewed under the microscope with magnification from 100 to 500 times. The experiments showed that the rate of dissolution of the samples (without thermomagnetic treatment) in HF solution is not stable. It is established that there is a direct correlation between the stability of the dissolution rate of glass surface layers and the thickness of dissolved layer during one etching. The structure of glass surface layers becomes more compact being treated by constant magnetic field. The rate of flat glass dissolution after thermomagnetic treatment decreases by        5–15 %. It was also established that thermomagnetic treatment increases the microhardness of flat glass by 10–15 %. Thus, glass structure under the electromagnetic influence becomes more compact. A correlation between the microhardness of treated glass and the rate of its dissolution has been established. The higher is the glass microhardness, the lower is its rate of dissolution in HF solution. Generally, the higher is the value of vector’s magnitude of magnetic induction, treatment temperature and its duration, the more compact the glass structure becomes.