The small-scale test has several advantages, such as low cost, low risk, and short duration, and has been widely applied in aerospace and other fields. Taking the lower structure of a typical civil aircraft fuselage as the research object, this study conducted theoretical analysis and experimental methodology of scaling on the impact crashworthiness of civil aircraft structures. Using a dimensional analysis, the complex dynamics of the fuselage crash were simplified to identify key physical parameters and processes. The main objects, critical physical parameters, and physical processes involved in the aircraft crash were discussed, leading to the extraction of key basic physical parameters and the derivation of primary dimensionless numbers that control the crash response of the fuselage structure. Based on the Buckingham Π theorem, the scaling factor for civil aircraft crashes was derived, establishing the small-scale experimental methodology. A 1/4 scale experimental model was designed and fabricated, and an impact test at a speed of 6 m/s was performed. The velocity, acceleration, ground impact load, deformation, and failure modes of key components in both full-scale and small-scale crash tests were obtained and compared. The applicability and accuracy of the small-scale theory in the crash experiment of the civil aircraft fuselage frame section were verified. The results show that the deformation and failure modes of the frames and columns of the 1/4 scale model are in good agreement with those of the full-scale model. The peak crash load prediction error of the small-scale structure for the full-scale prototype structure is 14.4%, the peak seat acceleration prediction error is 14.8%, and the peak acceleration prediction error at the beam is 13.1%. The small-scale tests can effectively predict the deformation, failure process, and dynamic response of key parts of the full-scale prototype structure. Therefore, the small-scale test could be used to verify and evaluate the crash performance of civil aircraft structures.