Aim\ To research the NC content in double base propellant with Gel Permeation Chromatography (GPC) method. Methods\ The rate of peak value was used to detect the effect of average nitrogen content in NC for the quantitative conclusion. The effect of double polydispersity can be overcome by adopting the feed in large amount. Results\ When the feed in large amount are adopted

the difference of average nitrogen content of NC has no evident effect for the measurement accuracy of GPC. Conclusion\ The measurement precision and accuracy about NC content with GPC can satisfy the specification of standard.