Abstract: Using the self-developed visualization test apparatus, centrifuge model tests are carried out to study the macro-mesoscopic formation mechanism of typical landslide-type debris flows according to field tests on a debris flow. Based on the grain-size gradation of field tests and gravity ratio, the centrifugal model tests are carried out under 20g. The soil samples are made up by silt sands and fine sands. The formation mode and soil-water action mechanism of landslide-type debris flows are analyzed from the macroscopic and mesoscopic points of view respectively by using the HD digital imaging equipment and the mesoscopic structure analysis software Geodip. The test results indicate that the centrifugal model tests can reproduce the phenomenon of the field tests approximatively. The formation mode of landslide-type debris flows is gradually collapsed in form of retrogradation to sliding. The reason of the formation of landslide-type debris flows is the shear strength failure of the slope caused by the rise of the pore water pressure and the seepage on the floor resulted from the motion of the fine particles with migratation of pore water in the slope.