Abstract: Initiation is one of the key problems of debris flow study. It is studied in this paper by the Vane rheometer which is a new apparatus for debris flow study, by which the stain, strain rate and strain acceleration are analyzed. Based on those analysis, the debris flow initiation process is defined. The initiation characteristics will be demonstrated after the initiation process was distinguished from others by this definition. In turn the debris flow initiation mechanism will be explained by the experiment results which show that resistance decreases and pore water presses increase during the acceleration process. Initiation mechanism can be explained as the results of debris effect, shear thinning and liquefaction by the experiment results combined with others studies.