The invention discloses a composite columnar water-bag prostate dilation catheter, which comprises a catheter main body. A catheterization cavity, an inner capsule cavity, an outer capsule cavity and a washing cavity are arranged in the catheter main body; the rear parts of the front openings of the catheterization cavity and the washing cavity are provided with a composite columnar high-pressureaqueous capsule; the composite columnar high-pressure aqueous capsule comprises an inner capsule and an outer capsule; the inner capsule is located at the rear section of the outer capsule; the frontends of the inner capsule cavity and the outer capsule cavity are opened in the inner capsule and the outer capsule respectively; the inner capsule is shorter than the outer capsule and located at the rear end of the outer capsule; during treatment, the inner capsule is expanded so that the urethra and the prostate on the part are dilated, while the neck of a bladder is kept at original state so as to conveniently control slide in the catheter. The expanded outer capsule is in a columnar shape so as to ensure the expansion effect and form a urethra gap with a size basically the same as the dilation diameter at the bladder neck.