Left-right hand parallel thread couplers are mainly used for rebar connection in scenarios where both rebars are non-rotatable and construction space is limited. Quick centering and butted connection of rebars can be achieved merely by rotating the coupler without turning the rebars themselves, which effectively solves the construction difficulty of traditional couplers in confined parts such as beam -column joints and walls. Featuring convenient construction, high installation efficiency, reliable connection performance as well as excellent slip resistance and fatigue resistance, these couplers can fully adapt to various rebar connection conditions of cast-in place and prefabricated assembled structures, greatly improving the on site construction efficiency and the stability of splice quality.