The invention relates to a high-speed earthing switch and an earthing switch assembly unit with the high-speed earthing switch. The high-speed earthing switch comprises a sulfur-hexafluoride arc-quenching device which is placed in a closed gas chamber of a shell body of the corresponding assembly unit in use. The sulfur-hexafluoride arc-quenching extinguishing device comprises a static end assembly part and a dynamic end assembly part. The static end assembly part comprises a static end support, a static end conductor arranged on the static end support and a static arc touch electrically connected to the static end conductor, the static end conductor is provided with conducting rod connection structures for being fixedly electrically connected with the adjacent ends of two corresponding conducting rods, the static arc contact is vertically arranged, the dynamic end assembly part comprises a dynamic end support and a dynamic arc contact which is combined with the static arc contact in a switch-on mode to enable the corresponding failure phase to be earthed, and the high-speed earthing switch further comprises an operating mechanism, wherein a power output end is connected with the dynamic arc contact in a transmission mode. The high-speed earthing switch and an earthing switch assembly unit with the high-speed earthing switch are provided for quenching the secondary arc current.