Abstract: According to the results of the stress test of four test piles in an extra-long bridge experimental zone, the paper analyzed the bearing capacity and the changes of settlement of conventional piles and post-grouting piles. The results show that under the same geological conditions, post grouting at the tip of bored pile could enhance the ultimate bearing capacity of single pile by improving the bearing capacity both at the tip and on the sides, and diminish the settlement, which optimizes the pile foundation.