OBJECTIVE: To explore the optimum harvest time of the Mongolian medicine, Radix Aconiti kusnezoffii herbs, by analysis of the changes of the main components in different developmental stages. METHODS: HPLC was used to determine the contents of the main alkaloids in 6 kinds of Radix Aconiti Kusnezoffii which were harvested in sprouting stage, early flowering stage, flowering stage and withering period, respectively. Taking the content of total alkaloids as index, the appropriate harvest time of Radix Aconiti kusnezoffii was determined. RESULTS: From germination to withering period, the total alkaloids in the 6 kinds of Radix Aconiti Kusnezoffii displayed increasing and then decreasing trend. The highest contents existed in the early flowering stage and the lowest existed in the withering period. The contents of the main components were sorted from high to low in the early flowering stage, germination stage, flowering stage and withering period. CONCLUSION: Based on the unique processing METHODS in Mongolian medicine and clinical medication safety, the withering period of Radix Aconiti Kusnezoffii is the best harvest time and this is consistent with the traditional Mongolian harvest period.