The absorption, fluorescence and time-resolved fluorescence spectra of Rhodamine 101 dye in both methanol and acidic methanol solutions were measured. The authors achieved the characteristic information of the absorption and fluorescence spectra, and obtained the S1 lifetimes. The authors assigned vibrational modes of the Rhodanmine 101 dye molecule through spontaneous Raman spectrum, infrared spectrum, and density function theory calculation. This work systemically characterizes the spectral, molecular structural, and vibrational information of Rhodamine 101 dye molecule, and provides necessary information for the application of Rhodamine 101 dye in dye sensitized solar cell and biological fluorescence marker.