Abstract: This paper briefly described the deposition regularity of silicon on catalyst during coker naphtha and/or diesel hydrofining. The silicon content at different positions of catalysts bed during hydrofining of coker naphtha, coker naphtha and diesel and liquid phase diesel were analyzed. The results show that the silicon deposition in catalyst bed of coker naphtha hydrofining reactor is evenly distributed, while the silicon deposition in catalyst bed of liquid phase diesel hydrofining reactor is decreased layer by layer sharply. Moreover the deposition situation in coker gas and diesel mixture hydrofining is between the two before.