The invention discloses a diamond space oblique steel column. The diamond space oblique steel column comprises foundation columns, oblique columns and transitional columns fixed among the foundation columns and the oblique columns; each foundation column comprises foundation column flange plates and ventral plates which are fixed in an in-column space formed by multiple foundation column flange plates in an enclosing mode, the ventral plates comprise the first ventral plate and the second ventral plate which are arranged in a crossed mode for fixation, and the two ends of the first ventral plate and the two ends of the second ventral plate are welded to center lines of the adjacent foundation column flange plates; each transitional column comprises a transitional column flange plate and a transitional column partition plate located in the transitional column flange plate, each transitional column flange plate is of a wide-end-up structure, the width transitional position of the transitional column flange plate is of an arc-shaped structure, and the width of the bottom end of each transitional column flange plate which is connected with the top end of the corresponding foundation column flange plate is the same as that of the corresponding foundation column flange plate.