The invention discloses a method for stopping a leak from the bottom of a steel casing on an inclined rock surface. The method comprises the following steps: (1) beating the steel casing in an underwater rock layer; (2) drilling by utilizing an impact drill; (3) beating the steel casing which is heightened through jointing into a hard rock layer at the water bottom; (4) manufacturing an inner steel casing and a vacuum cylindrical capsule; (5) lifting the inner steel casing together with the vacuum cylindrical capsule into the steel casing; (6) swelling the vacuum cylindrical capsule through grouting, so as to enclose the outside of the bottom of the steel casing; and (7) continuing drilling and completing the construction in the steel casing. The method disclosed by the invention is rapidand efficient; the construction cost is low, the steel casing can be stably fixed, and the bottom blocking effect is good; the problem that the steel casing is difficult to fix and the bottom of the steel casing is difficult to block when the inclination of a riverbed is greater than 30 degrees, the rock layer is shallow and hard, and no overburden layer is formed on the surface of the rock layeror a silt layer serves as the overburden layer can be solved; and accordingly, the mud leak in the drilling process can be avoided, the construction quality can be greatly improved, the construction period can be shortened, and the construction cost can be reduced.