The invention relates to a method for pressing circular tubes by an oil press in the shipbuilding process, which comprises that: 1, an upper die and a lower die are designed, the upper end face of the upper die is provided with arc grooves corresponding to the diameter of a circular tube to be pressed, the upper die is fixed with a pressure head of the oil press, and the lower die is locked on a press platform of the oil press by a limit block; and 2, press lines of which the interval is 50mm are marked along the length direction of a plate, the plate which is prepared and marked with the press lines on the lower die is flatly placed, the pressure head of the oil press drives the upper die to run downwards and act on the press lines, the action is repeated to press the positions of various press lines, the plate is gradually pressed into a semi-finished product circular tube of which the middle is reserved with a gap of 20mm, the gap of 20mm of the semi-finished product circular tube is sealed, and fixed by welding, and the semi-finished product circular tube is welded and corrected to finally form the circular tube. The method only needs one oil press, and is matched with special dies to process the circular tubes, and not only reduces the dependency on a special tube-rolling machine, but also can improve the wall thickness of rolled tubes, reduce the requirements on equipment configuration of shipyards and shorten the shipbuilding period.