The polarization of the output light emitted by ultraviolet-visible spectrophotometer is systematically measured, and its influences on the measurement of the absorption coefficients of the colored dissolved organic matter (CDOM) and particles are researched. The results reveal that the output light of the ultraviolet-visible spectrophotometer has significant polarization. Yet, the polarization of ultraviolet-visible spectrophotometer light has negligible influence on the measurement of the absorption coefficients of the CDOM and particles.