[Objectives]  Color formation in artificially cultivated Ophiocordyceps sinensis was investigated in order to improve the quality of this economically important product. [Methods]  The sclerotium of wild and artificially cultivated O. sinensis were observed before stroma development with HE staining, and tested to determine its malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content. In addition, polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), trypsin (TRY), amylase (AMY), invertase (INV), lipase (LIP) and attacin (ATT) activity levels, were assessed using ELISA-based methods. [Results]  Before the stroma development stage, sclerotium cell size and cell density were highest in Chongqing artificially cultivated O. sinensis (CQ), followed by carrot fed O. sinensis (H), and lowest in wild type O. sinensis (WT). In artificially cultivated O. sinensis, significant differences were observed in the activity of enzymes involved in the reactive oxygen metabolism, immune tolerance metabolism and MDA and H₂O₂ content regulation. Compared to the WT, PPO, SOD and POD activities were higher in the CQ and H treatment groups, whereas CAT activity was lower. However, of these changes, only the increase in SOD activity was significant. The activities of enzymes involved in reactive oxygen metabolism in the H group underwent significant changes, especially PPO and SOD activity, which increased by 37.19%, and 23.98%, respectively. MDA and H₂O₂ content in the CQ and H groups decreased significantly, whereas the TRY, AMY, INV, LIP, and ATT activity increased, although only the increases in AMY and LIP were significant. [Conclusion]  Color formation in artificially-cultivated O. sinensis is related to the reactive oxygen metabolism and immune tolerance metabolism. These findings provide information that can improve the quality of artificially cultivated O. sinensis.