The invention provides an anti-maloperation method for 50Hz harmonic protection for a direct current line. The method comprises the following steps: (1) executing a conventional 50Hz harmonic protection function; (2) judging whether an alternating current busbar voltage of a convertor station generates a second harmonic or not; (3) judging whether an excitation surge current is generated or not, if the judgment result is positive, turning to the step (4), or else, returning to the step (2); (4) judging whether the second harmonic on a rectifying side of the direct current line is generated by the excitation surge current or not; and (5) adjusting a 50Hz harmonic protection criterion and preventing protection maloperation. The anti-maloperation method provided by the invention can accurately judge generation of the excitation surge current and whether the direct current side harmonic is caused by the excitation surge current or not by an alternating current positive-sequence second harmonic voltage, does not cause a harmonic protection failure, does not need to add primary equipment, and is easily realized in a project.