In the foundation pit support engineering in Longhu of Qingdao, the retaining piles are set in soil layers of plain fill, coarse sand and silty clay. PRC-I 600AB110 single pre-stressed pipe pile, with high stiffness, was adopted as retaining pile, the pile diameter is 600mm, pile length are 7m and 8m respectively. After the excavation, no obvious cracks and subsidence appear in the ground at the top slope. The monitoring results show that the horizontal and vertical displacements of the foundation pit are within the allowable ranges, the construction has met the design requirements.