Inner support for deep foundation pit

A deep foundation pit inner support comprises a first fixing plate, a second fixing plate is fixedly connected to the first fixing plate, connecting plates are arranged in the second fixing plate and the first fixing plate, first limiting plates are fixedly connected to the connecting plates, and connecting frames are fixedly connected to the first fixing plate and the second fixing plate. A sleeve rod is arranged in the connecting frame, a clamping groove is formed in the sleeve rod, a threaded block is in threaded connection with the interior of the sleeve rod, clamping blocks are arranged in the deep foundation pit in a supporting mode, during dismounting, the clamping blocks on the two sides of the connecting frame are pulled, when the clamping blocks move, springs are extruded through second limiting plates, meanwhile, the clamping blocks are taken out of the clamping groove in the sleeve rod, and the clamping blocks are taken out of the threaded block. And during mounting, a second limiting plate is pus