In a continuation of investigation on Cordyceps militaris, thirteen compounds were isolated from the $CH_2Cl_2$ and n-BuOH-soluble fraction of C. militaris. They were identified as twelve diketopiperazines such as cyclo($small{L}$-Gly-$small{L}$-Pro) (1), cyclo($small{L}$-Ala-$small{L}$-Pro) (2), cyclo($small{L}$-Ser-$small{L}$-Pro) (3), cyclo($small{L}$-Val-$small{L}$-Pro) (4), cyclo($small{L}$-Thr-$small{L}$-Pro) (5), cyclo($small{L}$-Pro-$small{L}$-Pro) (6), cyclo($small{L}$-Thr-$small{L}$-Leu) (7), cyclo($small{L}$-Tyr-$small{L}$-Ala) (8), cyclo($small{L}$-Phe-$small{L}$-Ser) (9), cyclo($small{L}$-Phe-$small{L}$-Pro) (10), cyclo($small{L}$-Tyr-$small{L}$-Pro) (11) and brevianamide F (13), and an amino acid, tryptophan (12). Their structures were identified on the basis of chemical evidences and spectroscopic analysis including 1D-NMR ($^1H$, $^{13}C$), 2D-NMR (HSQC, HMBC) and MS spectral data. Among the isolated compounds, compounds 1, 2, 6-11 are first reported from C. militaris.