Abstract: Although the asymmetry of distribution parameters with random differences is common in distribution lines, the existing principle of single line-to-ground (SLG) fault protection is often studied on the basis of strictly equal three-phase distribution parameters. How to improve the reliability of SLG fault detection and arc suppression under asymmetric lines conditions is the key problem to be solved in SLG protection. This paper is based on the worldwhile development research of SLG fault protection. The formative factors for the existence of asymmetry in each feeder are firstly explained, and the influences of SLG fault protection on asymmetric distribution parameters are discussed based on the zero-sequence equivalent model, trajectory of zero-sequence voltage, and measurement of insulation parameters. Then, the influences of asymmetric three-phase distribution parameters on zero-sequence current and grounding current are verified respectively; moreover, the current status of existing research on SLG fault detection and arc suppression under the influence of asymmetry is sorted out and summarized. Finally, the research directions of SLG fault detection and arc suppression considering asymmetric distribution parameters are summarized for providing reference and suggestions for future research directions of SLG fault.