Abstract: The study on detecting,identifying and controlling the biological molecules in water is profound and significant project.We used the means of the resonance Raman spectra in the liquid-core optical fiber,and the intensity of the Raman spectra was enhanced 109 times.β-carotene was dissolved in organic solution(pyridine and water),poured into a number of hollow-core capillary made up of liquid-core optical fiber.The laser wavelength is 514.5nm.The laser power is 30mW.By this means we obtained the resonance Raman spectra of β-carotene with the concentration of 10-7mol/L～10-9 mol/L.This means provided an experiment technique for trace analysis of biological molecules in water.