With the boron addition, the Curie temperature of Sm2Fe17 permanent magnet was observed to increase from 130 degrees C and reach its highest value of 362 degrees C for the sample at x = 4. In the X-ray diffraction measurements, the peaks diffracted from the planes of hard magnetic Sm2Fe17 phase, observed in the sample without boron, disappeared with the boron addition and magnetic SmFe3 and Fe2B phases were detected. For all samples, the major peaks belong to the alpha-Fe phase. According to the magnetization measurements, the Ms value of the sample without boron is 155.52 emu/g, it decreased to its lowest value of 97.93 emu/g for the sample at x = 4. Boron addition resulted in an evolution of the phase constitution that caused changes in magnetic properties of the alloys.