The paper introduced a pile foundation engineering in limestone karst area, 364 cast-in-place piles were completed with the longest pile of 48m and largest pile diameter of 1.7m. Because of the complex formation, hole deflection, water inrushing, leakage and collapsing often occurred, and it was difficult to estimate the cave at the bottom of the pile hole and cave-penetrating. The difficulties were overcome by scientific judgment, strict prevention and careful treatment.