The effect of media composition and culture condition on mycelial growth and cordycepin (3'-deoxyadenosine) production was determined using Cordyceps spp. Among the strains of C. militaris and C. sinensis tested, C. militaris KCTC 6862, C. militaris DGUM 32003 and C. militaris KCTC 16932 were excellent for the production of cordycepin. The optimal temperature and pH for production of cordycepin were and pH ranged from 6.0 to 10, respectively. Among various sources of carbon and nitrogen tested, glucose and tryptone were very excellent for the production of cordycepin, respectively. After 5days cultivation with 1% of tryptone with nitrogen source, 39mg/l of cordycepin was produced. However, addition of phosphorus sources reduced the production of cordycepin.