The isotopic composition of the elements N and C of twelve Ophicordyceps sinensis samples and three Cordyceps hawkesii samples was determined by isotope ratio mass spectrometry. The statistical analysis results showed that the δ13C value from different regions were overlap,but the δ15N value ranges were different and distinguished in almost all of the samples( except sample from Hainan of Qinghai). The δ15N value from yushu and guoluo were significantly different from other regions( P < 0. 009). the δ15N and δ13C values between Ophicordyceps sinensis and Cordyceps hawkesii were significantly different. Therefore,Nitrogen stable isotope ratio analysis is useful in rapidly differentiating the geographical origin of Ophicordyceps sinensis. The method will have a wide application in tracing the origin of Ophicordyceps sinensis.