The effect of cooling rate on layering the deuterium ice inside inertial confinement fusion (ICF)spherical cryotarget is studied by backlit shadowgraphy. Experimentally, the temperature of ice is first determined by the calibration of temperature field around ICF cryotarget. The solidification process of deuterium in the cryotarget is in- situ characterized by backlit shadowgraphy. The power-spectrum density of the bright ring in shadowgraphy at different cooling rates is obtained. Experimental results demonstrate that the step-gradient slow cooling is favorable for forming uniform fuel ice in comparison with the rapid cooling. Furthermore, the validity of characterizing the ICF cryotarget layering by the backlit shadowgraphy is also verified.