As a kind of Phthalate esters ( PEs ), Di-n-butyl phthalate ( DBP ) is widely employed as plasticizers in the production of polymeric materials. The concentration variation of DBP/n-hexane solution was studied by monitoring the chroma evolution of infrared absorption spectra in conjunction with spectral analysis by using two-dimensional-correlation spectroscopy. Absorption peaks at 742, 1 078, 1 123, 1 281, 1 467, 1 728, 2 873, 2 933, 2 961 cm-1 was gained with Fourier transform infrared spectra. The IR spectra was divided into three bands: 400～1 200, 1 200～1 900 and 2 900～4 000 cm-1, correlation between the absorption peaks and the sequential order of the changes in spectral intensity extracted from synchronous and asynchronous plots indicated that some bong vibrations in 1 123 cm-1 (Benzene ring surface vibration and OCO bending vibration ), 1 728 cm-1 (CO bending vibration), 2 873, 2 961 cm-1 (CH3 concertina movement ) and 3 436 cm-1 (C—H bending vibration in plane of Benzene) is sensitive to the concentration of DBP. This result showed that the chroma evolution of infrared absorption spectra in conjunction with spectral analysis using two-dimensional-correlation spectroscopy can accurately analyze the concentration of DBP in n-hexane. This research provides a theoretical basis to the detection and analysis of DBP.