The invention belongs to the field of safety substation equipment technologies and particularly relates to a damping connection device applied to an indoor substation suspended GIS sleeve. The devicecomprises GIS cantilever sleeves, wherein the GIS cantilever sleeves are uniformly and fixedly arranged on multiple transverse supporting steel channels through supporting screws, the two ends of eachtransverse supporting steel channel are fixedly connected with pre-buried I-shaped steel through vertical suspenders, the pre-buried I-shaped steel is fixedly arranged in a production integrated building roof floor, the two ends of each transverse supporting steel channel are connected with one end of a diagonal steel tube, the other end of each diagonal steel tube connected with the corresponding transverse supporting steel channels is fixedly connected with the pre-buried I-shaped steel, and at least one damping energy consumption device is arranged on each diagonal steel tube. Through connection of the damping diagonal connection device and the suspended GIS sleeve, bad influences of multi-point earthquake input on the GIS cantilever sleeves and the suspenders can be effectively reduced.