The invention discloses a calculation method for short-circuit current in a two-phase or single-phase power transmission line. The calculation method comprises the following steps of: inputting a node impedance matrix, wherein since no actual current passes through a virtual node and the line, the ohm law is not violated when an arbitrary value is taken, the virtual impedance is an average value of known node impedance and inter-phase impedance of the virtual line is zero; calculating a three-phase line resistance matrix, wherein the line resistance is obtained by dividing percentage of a position of a fault point occupying the length of the line by basic line impedance and then multiplying by the node impedance matrix; solving a three-sequence line impedance matrix through relation between three asymmetric phasors and three groups of symmetric phasors; and solving the short-circuit current by the three-sequence line impedance matrix. The calculation method is essentially supplement of a part which cannot be calculated by a symmetrical component method, so that a symmetric component calculation method can also be used in the single-phase and double-phase power transmission line; the non-existing nodes and lines are substituted by virtual impedance which abides by the ohm law; and the application range of the conventional symmetrical component method is expanded by the calculation method.