The invention discloses a particle collection and shunting device and method in a filling medium seepage instability test. The device comprises a filtration chamber, wherein a first filter screen is arranged at the upper end of the filtration chamber; a flow guiding pipe is arranged at the lower end of the filtration chamber; at least one shunting pipeline is arranged on the flow guiding pipe; a second filter screen and a fluid monitoring element are sequentially arranged on each shunting pipeline; the shunting pipelines are communicated with a first collector; the tail end of the flow guidingpipe is directly communicated with a second collector. According to the device and the method disclosed by the invention, a lot of trouble in the previous test is solved, and quick collection and shunting of particles with different particle sizes in the filling medium seepage instability test are realized.