Abstract: The construction of super-high arch dams in China has taken the lead in the world. However, in the construction of some super-high arch dams, the transverse joints usually open after grouting. The causes, effects and treatment measures of secondary opening trouble the project construction. The secondary opening phenomenon of the joint after grouting in hydropower stations such as Dagangshan, Yangfanggou and JinpingⅠwas investigated, and the opening reasons, treatment measures and the safety impact on the arch dam were analyzed and discussed. The results show that after the joint grouting of the transverse joint, the dam body was in an unfavorable stress state when the water was not blocked or the water level was low, and the compressive stress on the transverse joint surface was relatively small. Affected by one or more factors such as construction disturbance, ambient temperature and autogenous volume deformation in the adjacent area, it will cause secondary opening. The ideal treatment effect can be achieved by adopting fine grinding cement grouting, chemical grouting and so on. After the water level raising, the arch compressive stress of the dam increases and the stress state of the transverse joint was improved. Therefore, the secondary opening of the transverse joint did not affect the long-term operation safety of the arch dam.