The use of dual light source difference technology can directly measure high-fluorescent substances, anti-interference, anti-noise, greatly improve the overall detection sensitivity and signal-to-noise ratio of the system, filter interference peaks (such as ambient light peak, PL peak, etc.), only retain pure Raman peak, capture small signal differences, under the premise of ensuring the accuracy of Raman peak measurement, can greatly reduce the power of the light source, eliminate the bad spot of the detector. Improve the reliability of the whole machine and spectral fault tolerance and error correction ability, through the combination of SERS technology, can achieve PPB level detection ability.