The JinpingⅠhigh arch dam with a height of 305 m is the highest under-construction dam of the world at present. The overall stability of the dam and foundation is a prominent problem due to the complex geological conditions in the dam site area. There are a variety of weak structural planes including faults, alteration veins, inner layer compressed zones, joint fissures and deep cracks. To make the dam be in much better stress state and meet anti-sliding stability and deformation stability of the skewback, a lot of reinforcement measures are adopted in the project. The main reinforcement measures include the left abutment concrete seating replacement, concrete grid and hole plug replacement, grooving replacement, and shearing resistant hole, etc. The overall stability of the dam abutment and the effects of dam abutment reinforcement are the important issues which must be concerned in practical engineering. The method of 3D geomechanical model test is adopted to carry out damage experiments. Two 3D models of JinpingⅠhigh arch dam are established respectively. One model is for the unreinforced scheme, and the other one for the reinforced scheme. Deformation distribution characteristics of the dam and foundation, failure mechanism and the overall stability safety degree derived from the two models are comparatively analyzed. The results show that, after reinforced, the symmetry of displacement of the dam body and dam abutments are significantly improved and the displacements are greatly reduced; the crack range and the damage extent of dam abutments are reduced under the same overload ratio, the overload coefficients to failure of the dam abutments are increased and the overload capacity is raised. The safety factors of overall stability obtained with comprehensive method are 4.7-5.0 for unreinforced scheme, and 5.2-6.0 for reinforced scheme. The safety degree is obviously improved through reinforcement measures. Comprehensive analysis shows that the main reinforcement measures, including the left abutment concrete seating replacement, concrete grid and hole plug replacement, grooving replacement, shearing resistant hole, applied to JinpingⅠhigh arch dam, are quite effective.