The invention discloses a method and system for determining carrying capacity of high-voltage cable lines, and relates to the technical field of electric transmission and distribution circuits. The method comprises the steps of generating a first current matrix for load current of each target high-voltage cable line on the basis of the load current; determining impedance of the current of each cable line so as to generate an impedance matrix; obtaining an allowable induced voltage amplitude value of each metal pipeline in at least one metal pipeline so as to generate a target matrix; determining allowable current of each cable line and generating a second current matrix; obtaining a plurality of element values of the same loop of each target high-voltage cable line, taking a minimum element value in the plurality of element values as a corresponding element value of a third current matrix and generating the third current matrix; and generating a fourth current matrix and taking the element value in the fourth current matrix as carrying capacity of at least one target high-voltage cable loop. According to the method and system, the safe operation of the metal pipelines and the personal safety of the operators and maintainers are ensured.