Accurate measurement of liquid–solid fraction of casting slab in the secondary cooling zone and precise prediction of final solidifying end of casting slab have momentous significances for internal defects improvement of continuous casting slabs, such as the segregation and shrinkage porosity etc. However, the on-line detection of slab solidification processing and final solidifying end haven't accomplished, which have been acknowledged as metallurgy problem all over the world. The paper presents a novel method, which called vibration method, to detect the liquid fraction and locate the final solidifying end of continuous casting slab. A physical simulation device using the materials of organic glass and water has been set up according to the similarity theory. Basing on theoretical deduction, physical experiment and numerical simulation, the research results provide guidance and reference for the on-line detection of liquid–solid fraction and final solidifying end of the slab.