Abstract: In order to reveal the influence of different post grouting methods on the bearing characteristics of cast-in-place piles, based on the self-designed pressure grouting system, the open-end, closed-end and composite grouting tests of three model piles (S₁, S₂ and S₃) located in homogeneous loess layer are carried out respectively, and the non grouting piles are set as the control. The vertical compressive load test is carried out 10 days after the grouting is completed. The grouting volume of S₁, S₂ and S₃ piles is 3 L, the grouting pressure is 0.3 MPa, and the grouting duration is 33, 47 and 44 s respectively. The test results show that the bearing capacity of S₃ is the largest after grouting, and the ultimate bearing capacity of the three piles is increased by 144%, 33.3% and 411% respectively; The lateral resistance of three grouting piles near the range of about 8 times of pile diameter from the pile end is enhanced, and the enhancement ratios under ultimate load are 170.7%, 39.5% and 233.2% respectively; After the static load test, dig out the model pile and observe the distribution of slurry on the pile side and pile end. It is found that the slurry of S₁ and S₂ piles returns up along the pile side, while for S₃ pile, in addition to some slurry returning up along the pile side, some slurry forms a cement enlarged head at the pile bottom.