Abstract: The reversible periodic magnetic focusing system according to the invention comprises a successive arrangement of permanent magnets 7 magnetized in the opposite sense, and pole shoes 1 interposed between the permanent magnets 7. Each pole shoe 1 is provided with a hole for passage of an electron flow. The holes of the pole shoes 1 receive grids 2 with meshes 3. The grids 2 are of a magnetically soft material and have a magnetic, thermal and electric contact with the pole shoes 1. Respective meshes 3 of the grids 2 are arranged coaxially.The invention stipulates ratios between the geometrical dimensions of components of the reversible periodic magnetic focusing system, which ensure passage of electron beams 5 through all the meshes 3 of the grids 2.The invention is applicable to the electronic industry where it can be used to design and manufacture, compact, low-voltage, superhigh frequency, high-power devices, such as klystrons and travelling wave tubes.