The invention discloses a DC resistance selection method and system for a complex power distribution network comprehensive optimization device. The DC resistance selection method comprises the following steps: 1) constructing positive-sequence, negative-sequence and zero-sequence three-sequence fundamental frequency equivalent circuits and equivalent circuits at a sampling frequency for the complex power distribution network comprehensive optimization device; 2) constructing positive-sequence, negative-sequence and zero-sequence three-sequence equivalent circuits at a fundamental frequency anda sampling frequency of a power distribution system at a fault point; 3) calculating to obtain a relationship between fault current and DC resistance; 4) determining a lower limit value of the DC resistance; 5) calculating to obtain a relationship between the current of the sampling frequency at the fault point and the DC resistance; 6) determining an upper limit value of the DC resistance; and 7) obtaining the DC resistance according to the lower limit value and the upper limit value as well as a relationship between the lower limit value and the upper limit value. The DC resistance selection method and system disclosed by the invention have the benefits that a selected DC resistance value can take into account effective arc suppression and accurate line selection of the power distribution system, effectively improve the control performance of the comprehensive optimization device and realize the substitution effect on an arc suppression coil.