The invention discloses a judging method and system for stability of a high-voltage electricity transmission iron tower foundation in a mountain area. The method comprises the steps that 1, the high-voltage electricity transmission iron tower foundation in the mountain area is tested, and affecting factors affecting the stability of the tower foundation are obtained; 2, the weight of each affecting factor in the stability of the tower foundation is analyzed through an analytic hierarchy process; 3, each affecting factor is graded and quantized; and 4, the instability index S of the tower foundation is calculated out, comparison is carried out, and a judging result for the stability of the tower foundation is obtained.