The present paper reports a dual wavelength spectroscopic method for the determination of chemical oxygen demand(COD) of low content samples, based on the absorption measurement at 440 and 560 nm. Since the absorptivities of Cr3+ at these two wavelengths are the same, a net absorption from dichromate ions can be determined by subtracting the absorption at 560 nm(only contributed by Cr3+) from the absorption at 440 nm. The results showed that the detection limit of quantification is 8.6 mg·L-1 and the relative standard deviations are in the 2%～15% range for the low COD standard samples (≤100 mg·L-1) in this proposed method. Further more, the method does not require calibration based on the standard samples. The present method is simple, reliable, and accurate; it is suitable for the application in a mass testing for low COD samples.