The AlO_X tunnel barrier in Josephson junctions prepared by conventional thermal oxidation method is formed by diffusing high-purity oxygen into the surface of Al. But the tunnel barrier fabricated by this method is not completely oxidized, and the thickness of barrier is hard to control accurately. In this work, we use atomic layer deposition to grow Al₂O₃ tunnel barrier on the surface of Ti. The sandwich structure of Ti/Al₂O₃/Ti Josephson junction is grown layer by layer. We investigate the corresponding microstructure and electrical properties by adjusting the thickness of the Al₂O₃ tunnel barrier and the area of the junction. The experimental results show that the monolayer Al₂O₃ film is about 1.17 Å (1 Å = 10^–10 m), which is grown by atomic layer deposition, achieves atomic-level controlled thickness. The resistance is controlled by adjusting the barrier thickness at room temperature. And we obtain a Josephson junction with good resistance uniformity at room temperature by optimizing the junction area.