The invention discloses a method for purification culture of sweet potato rot stem nematodes, which comprises the following steps of: (1) picking older young female and male nematodes in the rot stem nematode by a needle and placing on a container standby; and (2) transversely or vertically cutting the whole potato, perforating holes on one cross section, injecting little sterile water into each hole in a standard that the water does not overflow from the holes, then, inoculating the rot stem nematode, one older young female and two males, obtained in the first step into the small holes, then, covering the cut potato blocks onto the potato blocks inoculated with the rot stem nematode as a natural moisture preservation cover, sealing the edge gaps by paraffin wax, placing the potato blocks into a culture box after being bound by elastic materials, carrying out culture for 30 days at 25 DEG C, and obtaining a plurality of pure rot stem nematodes. The method provided by the invention is simple, the operation is easy, the workload is low, more importantly, the purity of the obtained group is high, the vitality is good, and the assurance is provided for the systematic study work on the biological characteristics, the pathogenic mechanisms, the population groups, the individual genetic variation and the like of the nematode.