The invention discloses a method capable of improving the direct starting cast-on success rate of low-carbon low-silicon-aluminum killed steel. In the converter working procedure, molten steel comprises, by mass percent, 0.03% to 0.06% of Si and 0.02% to 0.05% of Al; in the refining working procedure, the output molten steel comprises, by mass percent, 0.06% to 0.08% of Si and 0.015% to 0.035% of Al; the aluminum supplementing operation is finished before the refining middle period, and before 15 min of calcium treatment, aluminum supplementing operation is forbidden; the molten steel comprises, by mass percent, 0.004% to 0.0055% of Ca; before large ladle cast-on operation of the continuous casting working procedure, after a medium ladle vehicle reaches the position, middle ladle gas exhausting is carried out, and meanwhile a calcium line is put into a middle ladle impact area and middle ladle baking holes; after large ladle cast-on operation, when the liquid face height of the middle ladle molten steel reaches 250 mm, a covering agent is rapidly put into the medium ladle, and after the medium ladle molten steel reaches the starting cast-on liquid level face height being 350 mm, medium ladle cast-on operation is carried out. The direct cast-on success rate of the low-carbon low-silicon-aluminum killed steel produced by a small-billet continuous casting machine can be greatly improved.