In the present paper, studies on in-situ Raman spectra at high pressure up to 12.85 Gpa were performed on β-carotene using a diamond anvil cell (DAC), and the effects of pressure on the characteristic peaks and π-electron delocalization of β-carotene were discussed. The results showed that Raman frequencies of the main characteristic peaks of β-carotene shifted to high wavenumber with the increase in pressure. The relation between pressure and the three main characteristic peaks of β-carotene was given as follows: ν1(CC)=4.74P+1 511.4, ν2(C—C)=2.55P+1 157.6 and ν3(CH3)=2.25P+1 011.3. Under the pressure of 5.38 GPa, Raman spectrum of ν1+ν2 sum frequency of β-carotene was subjected to cleavage. Fuethermore, the degree of π-electron decolization was reduced with the increase in pressure, leading to CC double bond more compressible than C—C bond on the main chain of β-carotene.