Under the action of corrosion, abrasion and erosion of surface water and groundwater, the fine rock particles migrate with water and are gradually lose mass, which seriously deteriorates the internal structure of rock mass, causing seepage disasters. It is important to study the effect of mass loss on the seepage property of a broken rock to understand its engineering behavior. Consequently, an experimental system for testing the seepage property of broken rock under the condition of mass loss was designed, and it also could provide the variations of mass loss and porosity. A genetic algorithm of non-Darcy flow was constructed to characterize the seepage properties of broken rock. The effects of mass conservation and mass loss on the seepage properties of broken rock with different Talbot gradation indices were discussed. The results showed that the migration of fine particles in the internal structure of broken rock caused the fluctuations of permeability parameters even in the case of mass conservation. Under the condition of mass loss, the pore structure and framework structure of broken rock were damaged by the gradual loss of rock particles, which resulted in the gradual variation in the seepage property of broken rock. The broken rock specimen with smaller Talbot gradation index lost more easily rock particles. And the permeability of the broken rock specimen under mass loss was negatively correlated with the Talbot gradation index. It indicated that the broken rock with the finer particles caused more easily an unstable structure.