The invention discloses a no-leveling cylinder foundation for offshore wind power jacket construction and a mounting method. The no-leveling cylinder foundation comprises an offshore wind power construction jacket horizontally arranged on a seabed surface, and a cylinder foundation for fixing the offshore wind power construction jacket. The cylinder foundation comprises sleeves; the sleeves comprise outer walls positioned on the outer sides, and guide reinforcing ribs with a guide function; the outer walls and the guide reinforcing ribs are sealed as an integral structure through a baseplate; three sets of sleeves are provided in a triangle form, or four sets of sleeves are provided in a square form; the adjacent sleeves are fixedly connected with sleeve sets through reinforcing support rods; and the sleeve sets are fixed at the upper part of a cylinder through an A form or a B form. The no-leveling cylinder foundation has such advantages as accurate positioning, fewer procedures, improvement of the working efficiency and fewer used ship machines, is suitable for various sea areas with clay and sand stratums, and in particular, is suitable for the foundation offshore wind power jacket construction with limited application of steel pipe piles caused by such factors as far sea deepwater and higher buried depths of bearing stratums.