Invention relates to production of catalytically active magnetically separable nanoparticles. Proposed method comprises synthesis of nanoparticles using compounds of transition metals. Synthesis consists in thermal decomposition of iron acetyl acetonate in the presence of polyphenilethylene pyridil dentrones or dendrimers of second, third or fourth generation with the group of dicarboxylate at focal point at heating to 60??C at the rate of 10??C to complete dissolution of dendrone of second generation with dicarboxylic group and/or dendrone of third generation with single carboxylic group and/or dendrimers. Then, heating is performed to 300??C and held for 1-2 hours with subsequent cooling to room temperature, flushing and settling by ethanol, dissolution in chloroform and reaction product treatment by the solution of transition metals and their reduction by hydrogen and/or sodium borane and/or super hydride.