Abstract：The reinforcement effects of Lijiaxia arch dam on complicated rock foundation are studied. The reinforcement measures include concrete grid replacement in faults，cement grouting in weak rocks，water drainage and huge-ton reinforcement of anchorages with high performance tendons，etc.. A nonlinear constitutive model that is based on Drucker-Prager(D-P) criterion with damage elasto-plasticity finite elements is proposed to study its stability evaluation with the monitoring results of ten-year dam prototype monitoring. A back analysis of stress-strain distribution of Lijiaxia arch dam is also conducted. The stresses，strain and stability between numerical analysis and prototype observations of the dam show good coincidence. It is concluded that：(1) The factors of safety and the load-bearing capacity of both abutments are increased with reinforcement of rock foundation. The loading of the dam will be transferred to both abutments of the river，and the whole loading and point safety are evenly distributed. (2) The opening cracks appear in dam heel at the 2nd-stage water load with K1 = 2.0P0(P0 denotes normal water load)；K2 = 3.5P0；and the ultimate bearing capacity of dam nonlinear deformation appears in downstream surface at K3 = (5–7)P0，and the limit loading (7.0–8.5)P0. (3) The gold triangle of rock mass of left abutment is stable under normal water load；which is proven with numerical calculation and in-situ data. (4) The dam worked normally in the last ten years.
