The chemical compositions of Manihot esculenta crantz(M. utilissima Pohl)stalks were investigated, the contents of phenolic hydroxyl group and UV spectra of lignin were determined by ultraviolet-visible spectrophotometer. The result showed that the chemical compositions of Manihot esculenta crantz(M. utilissima Pohl)stalks were as follows: ashes 4.97%, cold water extraction 12.04%, hot water extraction 12.57%, 1% sodium hydroxide solution extraction 34.16%, benzene-alcohol solution extraction 4.20%, nitric acid-alcohol cellulose 35.86%, holo-cellulose 72.62%, pentosan 19.20%, acid-soluble lignin 2.51%, acid-insoluble lignin 26.10%, organic solvent-soluble lignin 1.07%, pectin content is 0.02%; it can be used as a non-wood renewable source of natural products.Phenolic hydroxyl content of organic solvent-soluble lignin and acid-insoluble lignin are 1.245 mmol·g-1 and 0.261mmol·g-1 respectively; the maximum absorption wavelength of organic solvent-soluble lignin and acid-soluble lignin in the UV region is near to 205 nm and 280 nm, but shifts to long wavelength or short wavelength with the nature of the different solvents.