Objective: To investigate the infrared fingerprint differences between different parts of Cinnamomum cassia and their essential oil

and provide a reference basis for studying their chemical composition characteristics. Method: The Fourier transform infrared spectroscopy (FT-IR) method and second derivative infrared spectroscopy (SD-IR) were used. Result: The holistic shape of peaks was similar in the FTIR spectra of the bark

branch and leaf of C. cassia. The structural information of the samples indicated that all of the three parts contained calcium oxalate

polyphenols and polysaccharides. The characteristic peaks of branch and leaf were stronger than that of bark at around 1 653 cm-1 and 1 734 cm-1

which proved that the quantity of saturated fatty acid esters and flavones in the branch and leaf was higher than that in the bark. At the range of 1 480-1 435 cm-1 and 1 630-1 580 cm-1

the spectra of branch showed two characteristic peaks

while the leaf showed only one peak at the corresponding site in second derivative IR method. The IR spectra of the essential oil of bark

branch and leaf was akin to that of cinnamaldehyde. The similarity calculation results showed that the content of cinnamaldehyde in essential oil was in the order of bark > branch > leaf. Near 1 734 cm-1

the peak intensity of essential oil in branch and leaf was stronger than that in bark

which indicated that essential oil of branch and leaf contained ester compounds of other structures. By comparing the conditions of the peaks around 1 275 cm-1 in the second derivative spectra

the essential oil in branch and leaf was further distinguished. Conclusion: The FT-IR and SD-IR can not only analyze the differences in holistic chemical constituents in different parts of C. cassia and their essential oil

but also can identify the different parts with similar components.