The invention discloses a multi-step pressure reducing and dewatering control method for a high confined water stratum deep and large foundation ditch. Multiple waterproof curtains are additionally arranged outside the foundation ditch, the first waterproof curtain is also taken as a foundation ditch retaining structure, modes such as an underground diaphragm wall, a bored secant cast-in-place pile, a plain concrete wall, double-row mixing piles and a high-pressure jet grouting pile can be adopted by the waterproof curtains, meanwhile a certain number of dewatering wells are arranged between waterproof walls, the dewatering wells are opened according to the needs, water head differences on the two sides of the waterproof walls are distributed in a stepped mode, the purposes that the numberof seepage paths is increased, the water pressure difference borne by the foundation ditch retaining structure is reduced, and the bursting risk of the bottom of the foundation ditch is lowered are achieved, and the destructive influence on surrounding important buildings is avoided.