To investigate the effect of grouting defects on the connection performance of prefabricated grout anchor lap joints, 39 grout anchor connection specimens with different positions and lengths of defects were tested using uniaxial tensile tests. The influence of grouting defect types and degrees on the stress performance of grout anchor connections was studied. The results show that when the defect level does not exceed 40%, the distribution type of defects has little effect on the stress performance of the grout anchor connection. For various types of defect specimens with defect levels of 50% and 60%, the peak load from large to small is the discrete defect, end defect, and middle defect. The most important thing to avoid in practical engineering is the defect in the middle of the grouting material, followed by the discrete defect of the grouting material, and finally the defect at the end of the grouting hole. The turning point of the comprehensive displacement ratio trend reflects that as the degree of defect increases, the failure modes of the specimens change from steel bar failure to bar pull-out.