Abstract: Bottom sediment of piles is often thick and impossible to clear completely because of the limitation in construction techniques of bored cast-in-place piles. It will reduce the bearing capacity of piles. The base post-grouting techniques inject cement slurry into pile bottom with its embedded pipe in order to reduce the detritus of pile bottom sediment and improve the bearing capacity of foundation piles. Combined with the static load test results of two piles with or without base post-grouting, the bearing performances of piles are analyzed comparatively. The load transfer mechanism and the behavior of base resistance and skin friction resistance of the piles before and after post-grouting are studied by the comparisons of the test results with the stress gages embedded in the pile shaft. The results show that the base post-grouting technique can improve the base resistance and the skin frictional resistance, and reduce effectively the settlement of foundation piles. The ultimate vertical bearing capacity of piles with base post-grouting is much larger than that without base post-grouting.