The over-sized Φ500 mm TC18 titanium alloy bar for aviation were successfully prepared in this paper. The uniformity of microstructure and stability of mechanical properties were systematically analyzed. The results show that the range of the major elements at different positions of head, middle and tail of TC18 bar is less than 1000 ppm which shows a uniform distribution of composition. The macrostructure at the different position of the bar is fuzzy, while the microstructure shows a common duplex structure indicating a uniform microstructure with high consistency. The mechanical properties of the bar at different positions show little difference with high stability satisfied the aviation.