A foldable baby carriage frame which includes a handle assembly, a front leg assembly, a front leg support assembly, a rear leg assembly, a rear leg connecting assembly, a horizontal support rod and a torsion spring. The torsion spring is provided at the connection between the front leg support assembly and the rear leg connecting assembly, and the torsion spring controls the opening and closing of the front leg support assembly and the rear leg connecting assembly by the rotation. When downward force is applied to the rear leg assembly, the rear leg assembly pivots downward with the torsion spring as the pivot point, so that the front leg support assembly and the rear leg connecting assembly realizes the effect of automatic folding. After the downward force is released, the front leg support assembly and the rear leg connecting assembly return to the state when the baby carriage is in use.