Abstract: Using the self-developed visualization test apparatus with constant slope and rainfall intensity, centrifuge model tests on rainfall-induced debris flow are carried out in order to study the formation mechanism of debris flow under different particle compositions. The test conditions include 20 times of gravity, five soil samples and different fine particle contents. Through the analysis of macroscopic displacement fields, moisture migration and pore water pressures under different particle compositions, different morphological characteristics of debris flow are observed and discussed. The test results indicate that the failure pattern of debris flow changes from retrograded sliding to whole flow sliding with the increasing content of fine particles from 10% to 70%. And the difference of permeability coefficient under different particle compositions is the major cause for different failure patterns of debris flow.