We have measured the UV-visible absorption and Raman spectra of β-carotene which contains 9 CC conjugated double bond polyenes biological molecules in 9 kinds of solvents.The results showed that the Raman scattering cross-section for C—C and CC stretching vibration bands of β-carotene increases linearly with the increase of solvent density.The mechanism is that β-carotene in high density solvent is less affected by perturbation,has higher structure order, more extended π electron delocalization，and stronger coherent weakly damping C—C bond vibration,which results in a large Raman scattering cross section.Studies on the influence of solvent density to molecular Raman cross section have not been reported.This paper is promising as on experimental hint on theoretical study of light scattering,and provides a reference for research of polyenes chain molecules and the development of optoelectronic devices.