This paper experimentally examined the effect of bulk density on the combustion behaviour of nitrocellulose with isopropanol humectant. Experimental findings reveal that when the bulk density varies within 120.5 approximate to 171.5kgm(-3), the fuel regression rate in the quasi-steady stage changes slightly, with an average value of 0.41mms(-1), while it will decrease visibly as the bulk density increases within 171.5 approximate to 209.7kgm(-3). The overall regression rate follows the similar variation trend. The measurements of thermocouples mounted inside the sample also support the findings above, and further indicate the flame temperature of nitrocellulose-isopropanol is about 600 approximate to 800 degrees C. Considering the measured radiative heat flux and flame height determined from flame intermittent contour, the radiation fraction of nitrocellulose-isopropanol is quantitatively ascertained, i.e. roughly equivalent to 0.3. It is expected that the findings could provide insights into the fire risks of nitrocellulose products with different bulk densities and further offer guidance on their safety management.