To investigate the peroxidase function and its signal pathway, activity and isozyme pattern of peroxidase and transcription level of the peroxidase gene rsprx1 and rsprx2 in Chinese red radish seedling (Raphanus sativus L.) were investigated after administration of the exogenous peroxidase (extract of radish). The activity and isozyme pattern of peroxidases were increased, among cotyledon, hypocotyl and root, the most significant increase of peroxidases activity was observed in hypocotyls, the activity of phenylalanine ammonialyase was also increased, but the pelargonidin content was decreased. Although the exogenous application of horseradish peroxidase and the extract of radish could both affect the activity of endogenous enzyme and metabolites of Chinese red radish seedlings, the latter was more effective than the former. Nifedipine, as L-calcium channel blocker, affected the activity of peroxidase and pelargonidin content in Chinese red radish seedling. Exogenously added nifedipine with the extract caused reversal of the effects. It is concluded that calcium was involved in the signal pathway of the extract of radish in Chinese red radish seedling.