The invention discloses a high-voltage direct-current grounding electrode line differential insulation matching method based on a safety region method, which comprises the following steps: firstly, respectively establishing parallel gap dimension curves along a grounding electrode line, which are corresponding to the internal overvoltage peak value, the grounding electrode line insulation level, lightning preventing arcing and natural arc extinguishing in each position of the grounding electrode line; then, constructing a safety area according to the parallel gap dimension curves along the grounding electrode line; obtaining a parallel gap size range of each position of the grounding electrode line; finally, formulating a differential parallel gap configuration scheme according to each section of the grounding electrode line. According to the method in the invention, multiple factors influencing the size selection of the parallel gap are comprehensively considered; it is ensured that the internal overvoltage does not cause the parallel gap flashover; the insulation level of the grounding electrode line is lower than the protection level of the neutral bus, so that lightning cannotcause parallel gap arcing or independent arc extinguishing after parallel gap flashover; the insulation coordination scheme of the grounding electrode line can be optimized in all directions; and thesafety, reliability and stability of the operation of the grounding electrode line are improved.