Abstract: A method for making slender seamless steel mold is disclosed, wherein the outer surface of a solid slender male mold is first chased with concave and convex stripes. Then, the male mold is hardened and fitted into a hollow female mold which has not been gone through hardening process. Thereafter, a hydraulic pressure is exerted onto the outer surface of the female mold so as to impress the concave and convex of the male mold onto the inner surface of the female mold. Then the male mold is annealed and drilled with a longitudinal through hole. At least three longitudinal slits are cut on the wall of the through hole in an outward direction. Finally, the male and female molds are together heat-treated and put into water with normal temperature in order to create fissures at the slit portions of the male mold and crack the male mold into pieces. Consequently, a slender seamless steel mold having inner surface formed with concave and convex stripes is completely made.