Abstract: The wall rock of the south line 6# tunnel of the project of abstraction from Yellow River at Wanjiazhai is the carbonatite stratum of the upper and lower Majiagou formations of Ordovician system, where karst well developed and formed mainly irregular water-eroded caves, while most of them are filled with karst breccias, detritus soil and low liquid limit muddy soil. For the engineering geological properties of these karst fillings are so bad as to induce deformations like the crack and slab staggering of the tunnel liner concrete domain, which will inevitably impact the normal water delivery of the tunnel. To solve this problem, geological radar testing, complementary drilling and sampling are done in the tunnel. Furthermore, the laboratory soil test is also done and wall rock's Karst up-growth characteristics are analyzed. Based on the engineering properties of the Karst fillings, cement grouting is used.