The invention firstly discloses a quickly-replaceable roller set of a straightener. The quickly-replaceable roller set comprises a driving shaft, a driven shaft, straightening rollers, a locking mechanism and an axial adjusting device. The locking mechanism comprises a threaded pull rod, a hydraulic cylinder and a driving mechanism, the hydraulic cylinder is used for applying locking force onto the straightening rollers, and the driving mechanism is used for driving the threaded pull rod to rotate. The invention further discloses a double-support type steel straightener adopting the quickly-replaceable roller set. The double-support type steel straightener comprises a framework, a plurality of quickly-replaceable roller sets, a driving device and a roller seam adjusting device, and the quickly-replaceable roller sets are arranged in upper and low rows and in a staggered manner. The double-support type steel straightener utilizing the quickly-replaceable roller set has the advantages of simple structure, safety, reliability, short roller replacement time, high work efficiency and adjustment accuracy and the like, and further, investment cost can be effectively reduced, straightening noise is reduced and product quality is improved.