A method to determine phytolith-occluded carbon ( PhytOC) was explored. Sodium hydroxide solution was used to dissolve the silicon compound(SiO2 ·nH2O) which occluding on the carbon, and then potassium dichromate-sulphuric acid solution was used to oxidize the released organic carbon. The concentration of Gr3+produced from the reaction was measured by spectrophotometry with its absorbance at 590 nm wavelength. The organic carbon concentration was calculated based on the amounts of potassium dichromate consumed. This analytical method was verified well accuracy and repeatability by running standard addition and recovery experiments. It has the advantages of low carbon loss, easy to operate, low cost;and hardly any influence to body health, as compared with acid dissolution-Elementar Vario MAX CN method. The results obtained from this method have a good correlation with these determined by Elementar Vario MAX CN ( Germany) .