In order to improve the bearing performances of bored cast-in-place piles in soft soil area, an end-side association post-grouting technology is proposed. Based on one highway bridge project, the composite post grouting and O-cell pile testing method on one cast-in-place concrete piles S1 are performed to study their bearing deformation characteristics and the improving effect of pile tip resistance and pile side frictional resistance. The research shows that pile side grouting has improved the mechanical characteristics of pile-soil interface and the pile tip grouting could strengthen pile end soil. The strengthening effects of pile shaft resistance in silty clay are in the range of 1.49–1.60 and the strengthening effects of pile tip resistance in gravel with clay is 1.71. End-side association post-grouting technology can effectively increase the axial bearing capacity of bored piles in soft soil and reduce the pile top settlement.