The invention discloses an ultra-low carbon aluminum killed steel molten steel treatment method and belongs to the technical field of iron and steel smelting. The ultra-low carbon aluminum killed steel molten steel treatment method aims at solving the problems that when ultra-low carbon aluminum killed steel molten steel is treated in the prior art, oxygen deficiency or high oxygen is generated easily during decarburization, molten steel inclusions are difficult to control, and the pourability is poor. The ultra-low carbon aluminum killed steel molten steel treatment method comprises the following steps that A, lime is added in a molten steel tapping process, and a slag regulating agent is added after tapping; B, high-alkalinity refining slag is added to a molten steel LF station, and theoxygen activity before the process of leaving the LF station is controlled to be within 800 ppm; and C, a molten steel RH station controls the oxygen activity of the molten steel to be within the range of 500 ppm-800 ppm, and the slag regulating agent is added during the process of leaving the RH station. By the adoption of the ultra-low carbon aluminum killed steel molten steel treatment method,the oxygen activity and slagging process of molten steel are properly controlled, the problems of insufficient oxygen and high oxygen during decarburization are solved, the state of molten steel inclusions is controlled stably, the refining processing capacity of the RH molten steel is improved, the pourability of the molten steel is improved, and the quality of continuous casting products is ensured.