The invention discloses a high-pressure-bearing water and thick sand and pebble formation deep foundation pit grouting bottom-sealing structure and a construction technology thereof. The high-pressure-bearing water and thick sand and pebble formation deep foundation pit grouting bottom-sealing structure comprises a waterproof curtain which is inserted into the ground; a slurry base plate, a slurry side wall and a slurry separation wall are formed below the waterproof curtain through grouting; the slurry side wall and the waterproof curtain are cemented closely; the slurry base plate, the slurry side wall and the slurry separation wall surround a base to form a plurality of U-shaped grouting cabins which are concaved downward; a slurry reinforcement layer is formed above the slurry base plate through secondary grouting. According to the high-pressure-bearing water and thick sand and pebble formation deep foundation pit grouting bottom-sealing structure and the construction technology thereof, the integral strength and stiffness of the pit bottom is increased through the U-shaped grouting cabin structure, the double functions of pit bottom reinforcement and seepage control are achieved, the problems of the effect on the stability of the pit bottom due to the buried depth increased high-pressure-bearing water and the pit bottom uplift caused by foundation pit excavation can be effectively solved, and meanwhile the lateral displacement of the pit wall and the settlement deformation of the surrounding environment are reduced well.