On the right bank of Wudu reservoir of Sichuan, silt and fine sand layer with thickness of 2.3～9.8m exposed in EL574m grouting adit; in this case, reliable anti-seepage curtain can not be formed by high pressure grouting with ordinary cement. By the use of a combined grouting method of high pressure jetting grouting, wet grinding fine cement and chemical grouting, good construction effect is achieved. The construction was tested by water pressure in borehole, high-power acoustic CT, single-hole acoustic wave and drilling digital panoramic imaging, which indicates that the construction has met the requirement of designed seepage control.