Based on existing research results on grout sleeve splicing for reinforced bars, insufficient grouting defects in actual projects were simulated by controlling artificially the content of grout. Monotonic tension tests were carried to study the performance of mechanical properties and deformation. High-stress reversed tension and compression test and large-deformation reversed tension and compression test were carried to study the mechanical performance under minor and major earthquakes respectively. The content of grout was the only influencing factor in the test. The thickness of grout above the bar reflected the level of the grout content in horizontal connection, the upper steel’s anchorage length reflected grout content in vertical connection. The test results show that two categories of failure pattern might happen, pullout or fracture of the bar, which was decided by the bond capacity, between the bar and the grout, together with the tensil capcity of the bar. The bond capacity is mainly affected by grout content.