A method for qualification and quantification of hexanitrohexaazaisowurtzitane (HNIW) by ultraviolet spectrophotometry was established. The solution of HNIW in ethyl acetate has the maximum absorbance at 272.3 nm by ultraviolet-visible spectrophotometer. The concentration of standard HNIW was correlated very well to its optical density at 272.3 nm in the range of 0-150 mg·L^－1 with a relativity coefficient of 0.9992. During the production of HNIW,sample was taken out of the reaction vessel and measured by spectrophotometer to determine the product by λ_max and the concentration of the HNIW was calculated according to the absorbance.