A Raman signal detection and analyzing system and a method thereof are disclosed. The Raman signal is generated by emitting an excitation light to a sample. The Raman signal is then modulated by passing through a plurality of optical filter and modulator. The resulting modulated Raman signal comprises two orthogonal components, which intensities are to be computed based on the first harmonic of said modulated Raman signal. The content of a specific analyte within the sample can then be determined based on the ratio of the intensities of the two components.