Flavours play a significant role in food and chemical industry in our daily life. Despite many flavour compounds having been identified and studied, the behaviours of volatility and sensory characteristics are still not fully understood. The release of flavours was found to be highly sensitive to plenty of factors, such as the nature of molecules, external environment, concentration of volatiles and non-volatile compounds. [1][2][3] Non-volatile compounds with long alkyl chain, such as fat, oil and lipids, have significant impact on the release of flavours. [4][5][6][7] The proportion, existential status and distribution of these compounds determine the flavour release, flavour stability and sensory characteristics. 2,6,8 Long-chain alkanes (LAs) are common unscented compounds that are found in many kinds of plant extract and essential oils. 9-11 Moreover, alkanes are proved to have an important impact on the flavour release and odour switch. 12,13 REO is one of the most valuable natural flavours. Not only being perfume or food additive, REO has also been proved the activities of antianxiety and antimicrobial. [14][15][16][17] The component of natural REO is extremely complicated, consisting of hundreds of chemical compounds. [18][19][20][21] As well as the volatile components, LAs are important constituents of REO. The relative content of alkanes and derivatives varies from 3% to 35% approximately according to the varieties and regions of REO. [22][23][24][25] Moreover, experienced perfumers frequently used alkanes for rose-flavouring process to regulate the odour.However, during past decades, the research of REO was focussed on the volatiles and aromatic compounds. Alkanes in REO were ignored to a certain extent. The existence and composition analysis of rose