The invention provides an adjustable guide frame suitable for construction operation of a steel protection cylinder. The adjustable guide frame is structurally composed of an upper layer of transverse beams and longitudinal beams, a middle layer of transverse beams and longitudinal beams and a lower layer of transverse beams and longitudinal beams; the longitudinal beams of the middle layer are longer than the longitudinal beams of the upper layer and the longitudinal beams of the lower layer and serve as cantilever rods; the two adjacent transverse beams and the two adjacent longitudinal beams of each layer are reinforced and connected through transverse inclined rods; the transverse beam and longitudinal beam structure of the upper layer is connected to the transverse beam and longitudinal beam structure of the middle layer through upper vertical rods and vertical inclined rods; the transverse beam and longitudinal beam structure of the middle layer is connected to the transverse beam and longitudinal beam structure of the lower layer through lower vertical rods; the upper vertical rods and the lower vertical rods are respectively of a hollow cubic structure, the length of outer sides of the lower vertical rods is smaller than the length of inner sides of the upper vertical rods, and the upper vertical rods and the lower vertical rods are connected through pin holes; and a mechanical jack for locating, correcting and adjusting the steel protection cylinder is arranged inside the guide frame. According to the adjustable guide frame, through the pin holes in the upper vertical rods and the lower vertical rods, the height of the guide frame can be freely adjusted, and therefore the guide frame can be suitable for more construction environments, and the construction accuracy of the steel protection cylinder at different construction water levels can be effectively improved.