The ZSH(DR)SED series ultra-low-temperature butterfly valve with maintenance opening uses a top-entry body design to reduce external leak paths and the influence of pipeline stress. The plug/disc and seat can be removed through the access opening for in-line maintenance. Separate, replaceable seat and sealing-ring structures and one-setup machining of the upper and lower shaft bores help ensure dimensional accuracy and bidirectional sealing. The stem packing uses double graphite sealing plus a live-loaded adjustable sealing structure. Fire-safe, antistatic and blowout-proof stem features are incorporated, and anti-loosening structures are used on the seat and seal retaining plates. An extended bonnet and drip tray protect the packing and stem from cryogenic media. Deep-cryogenic treatment during manufacture improves material structural stability at ultra-low temperature, helping prevent deformation caused by phase change and maintain sealing performance and service life.