Annular arched girders structural support system bears pressure mainly， which is conducive to play compressive strength of concrete materials reasonably and convenient to conduct construction. The single annular arched girders structural support system is suitable for regular pit whose aspect ratio is close to 1. For the irregular pit with large aspect ratio， double annular and even multi-annular support has been applied in some projects. An irregular “L” shaped foundation pit in Shanghai soft soil area with area of nearly 50 000 m2 and a maximum excavation depth of 13.15 m applied double annular support system. The foundation pit used top-down method and is designed into A， B， C three zones，where zone A applied double annular support system，zone C is supported by side girders and angle diagonal brace，and zone B uses angle brace to support， working as a transition zone. Based on in-site monitoring data， this paper investigated the movement of lateral wall， subsurface horizontal movements and surface subsidence. Based on these data， this paper summarizes the deformation and force bearing characteristics of double annular support system， which can provide valuable reference for applications of it in deep foundation pit engineering.