The invention relates to an unyoked series resonant reactor, which comprises a fixing plate, a winding and fixing rods, wherein an iron core is arranged in the center of the reactor, and is arranged in the reactor through the fixing rods. According to the unyoked series resonant reactor, a section of iron core is arranged at the central position of the reactor, so that the number of turns of a coil of the reactor is reduced under the condition of ensuring an inductance value; an unyoked radiation type iron core structure is adopted, the iron core is divided into a plurality of units, and each unit is provided with a plurality of pieces with different width specifications; the unyoked series resonant reactor is light in weight, small in size and low in energy consumption.