The invention relates to a simple cordyceps militaris strain rejuvenation method. The method comprises the following steps: hardening fresh, alive, complete and healthy silkworm chrysalis; cutting the back and abdomen of the hardened silkworm chrysalis to obtain 2-3 cuts respectively; laying the hardened silkworm chrysalis in an auxiliary culture medium in a mode that the back of the silkworm chrysalis is upward, and sterilizing at 121 DEG C for 20 min; inoculating a liquid strain, and performing mycelium culture and fruiting body culture; and then, performing tissue separation on the fruiting body growing from the cuts on the back of the inoculated silkworm chrysalis. In the invention, the silkworm chrysalis subject to high-temperature and high-pressure sterilization is adopted, and the strain rejuvenation is performed after properly increasing nutrient components and moisture; and compared with the traditional rejuvenation method adopting alive silkworm chrysalis injection, the method provided by the invention has the advantages of low pollution rate, high success rate, simple operation, high biological transformation rate of silkworm chrysalis, and the like.