Abstract: The quality of sleeve grouting construction is related to the uniaxial tensile mechanical properties of prefabricated component steel bar connection joints, and Important guarantee for the safety of prefabricated building structures; The sampling results after the full sleeve grouting construction indicate that the non compaction of the grouting materials the main reason for the quality defects of the uniaxial tensile mechanical properties of the sleeve connection joint.This article combines engineering field tests with laboratory tests, focusing on the mechanical properties of sleeve connection joints under different defect lengths, such as yield strength, tensile strength, and failure mode; he experimental research results show that when the grouting defect reaches 70% of the anchorage length of the upper steel bar, the failure mode of the steel bar changes from tensile fracture of the outer steel bar of the sleeve to pull-out failure of the steel bar; The post grouting process is carried out by injecting grouting material into the outlet through a needle tube.After 28 days of curing, the synergistic performance between the new and old grouting materials is good. The unidirectional tensile performance of the sleeve connection joint is close to the full state performance of the sleeve, and can meet the standard requirements.This proves that the post grouting process is feasible, stable, and has good repair effects.