The invention belongs to the field of an electric power system, in particular relating to a method for analyzing and optimizing the reliability cost/benefit precision of power supply. In the method, when a distribution network plan is carried out with the improvement of power supply reliability as a target, a reliability cost/benefit analysis curve can be obtained during individual implementation of each measure through actually analyzing various reliability improvement measures by utilizing the method; then the curves corresponding to the various measures are combined to formulate a reliability optimized strategy in combination with various measures by utilizing a classical reliability cost/benefit precision analysis theory of power supply; a reliability optimized path is selected from the combined curve by utilizing the strategy and can be further analyzed into the actual investment of each optimized measure, and further an implementation scale required for each measure can be obtained; and finally, the implementation scale is put into a specific scheme by combining the actual condition of a distribution network.