The compaction characteristics of broken rock in caving zone have a significant impact on the movement law of overburden and the prediction of surface subsidence. The mechanical properties of broken rock are clearly affected by the original rock strength of the roof. In this paper, the compaction mechanical behaviour of broken loose rock masses with different original rock strengths is studied by model testing. The results show that (1) the greater the original rock strength of broken rock is, the shorter the initial compaction stage, the earlier the transition compaction stage and stable compaction stage, and the lower the degree of compaction. (2) The initial deformation modulus and ultimate axial strain have a linear relationship with the original rock strength of broken rock. (3) Under different axial pressures, the deformation modulus increases with increasing original rock strength of the broken rock. The tangent modulus and axial stress change approximately linearly, the secant modulus and stress change linearly, and the tangent modulus and secant modulus have an exponential/hyperbolic relationship with strain.