Abstract: The backfill roof is an important load-bearing structure in underhand backfill stopes, and its stability is directly related to the safety of stope operations. Rational determination of the required roof strength is therefore essential for achieving safe, efficient, and economical production. This paper systematically reviews relevant research in China and other countries on backfill roof strength design methods and their applicability. First, the major failure modes of backfill roofs, including tensile, flexural, shear-sliding, rotational, caving, and compressive-shear failures, are summarized, together with their underlying mechanical mechanisms. Second, based on beam theory, plate theory, and limit equilibrium theory, analytical methods including the simply supported beam model, fixed-end beam model, thin-plate model, thick-plate model, Mitchell model, and modified Mitchell models are systematically reviewed, and the application of reliability theory to roof strength design is discussed. The applications of numerical simulation in identifying roof failure modes, validating analytical models, and evaluating strength requirements are further examined, together with the characteristics of empirical chart methods. The review shows that existing analytical models are generally based on idealized boundary conditions and simplified loading assumptions, with insufficient consideration of rock-mass closure and the resulting horizontal compression during deep mining. Numerical studies indicate that rock-backfill interaction can substantially alter the stress state and failure mode of the roof and may cause strength requirements to vary in ways that differ from those predicted by conventional beam and plate theories. Empirical chart methods are convenient for engineering applications, but their direct transferability between mines is limited by the small number of mine cases on which they are based. Future strength design of backfill roofs should further consider the coupling of multiple failure modes, coupled deformation between rock masses and backfill, variability in backfill strength, and long-term service effects. Greater integration of analytical theory, numerical simulation, laboratory testing, in situ testing, and field monitoring is needed to establish a multilevel strength design framework with clearly defined applicability conditions and a sound basis for parameter selection.