In view of the phenomenon that the surface of hydrofining catalyst on the top of hydrofining reactor was covered with scale when the diesel hydrocracking unit in a refinery was shut down,accompanied by replacing catalyst,the sampling analysis of hydrofining catalyst at different location was conducted.The specific surface area and aperture analyzer,carbon sulfur analyzer（C-S）,and scanning electron microscope（SEM） were carried out to analyze hydrofining catalyst after toluene extraction and regeneration.The results showed that the amount of carbon deposited on the deactivated catalyst at different location was relatively low,but the catalyst specific surface area and other pore structure parameters obviously decreased which was significantly lower near the top of hydrofining catalyst bed.The regeneration effect of hydrofining catalyst at different location was not ideal.The characteristic diffraction peak of AlPO₄ was appeared on the regenerated catalyst,and the inorganic impurities containing P,Si,Fe and little As elements deposited on the surface of hydrofining catalyst,or a little impurities diffused into catalyst channel,which was the main reason of catalyst deactivation.Along the top-down flow direction,the deposition of impurities on the hydrofining catalyst gradually decreased,and the deactivation degree of the hydrofining catalyst weakened.