Abstract: Fresh lily bulb was collected, steamed and pulped to prepare cooked lily sample (ZBH). Pure milk was disinfected, vaccinated and fermented for 12 h to prepare original-flavoured yoghurt sample (SN-1/2). Sample of lily yoghurt (SN-3/4) and samples of fermented lily yoghurt (BHSN) fermented for 8, 10, 12, 14 and 16 h separately were prepared from SN-1/2 and ZBH as described. Components in the volatile substances released from the 4 kinds of samples were determined by GC-IMS with head space sampling. On the base of the IMS data determined and referring to NIST database, 24 compounds were identified and characterized as the flavouring substances in the volatile substances of the 4 kinds of samples. And it was found by surveying the data of intensities of signal peaks of these compounds, that significant differences in contents of 15 among the 24 compounds were observed. Based on the characterizing components found in the volatile substances liberated from the 4 kinds of samples or on the differences of signal peaks, differentiation could be made among related samples. For instance, 1-hexanol was found to be characterizing components for ZBH. Furthmore, by applying the OPLS-DA for the flavouring substances of the samples, a clear distinction among the 4 kinds of samples was recognized and also the differences of species and contents of the main flavouring components found in the volatile substances liberated from BHSN samples fermented with different time were realized, on the base of which determination and selection of optimum fermentation time could be made.