The Raman spectra of formaldehyde, acetaldehyde, propionaldehyde and n-butyraladehyde （CnH2nO,n=1, 2, 3, 4） were obtained by portable Raman spectrometer. The molecules of the four aldehydes were calculated by density functional theory（DFT）. By comparing the calculated result and the experimental result, the bands of these Raman spectra were assigned. And the Raman spectra of these aldehydes molecules were analyzed and compared. These aldehydes could be real-time rapidly identified by Raman spectroscopy technology.