The invention discloses a seepage instability water inrush experiment device and method for an internal filling medium of fissure and fault type geological structures. The device comprises a test bench, a seepage experiment system, an axial pressure loading system, a hydraulic pressure loading system, an information monitoring system, a particle collection system and a flow monitoring system. In the invention, by virtue of the design of a seepage chamber, spatial characteristics of geological structures, such as fissures and faults, can be effectively reflected, and a test sample does not adopt a cylindrical shape, thereby accurately revealing the evolution characteristics and disaster-causing mechanisms of seepage instability water inrush of the internal filling medium of the geological structures; the seepage experiment system can freely rotate and can carry out a seepage instability water inrush experiment of the filling medium in different seepage directions; and the seepage chamber adopts semi-transparent or transparent side walls which are visualized, so that the change characteristics of the test sample in the experiment can be observed.