Among the three basic conditions for debris flow formation, solid source conditions are the most intuitive object for studying debris flow, and the most difficult to study but the most difficult to quantify. This paper discusses the definition of debris flow solid matter and gives a measurement method. The current research status of the investigation methods and methods of loose solid material reserves and dynamic reserves of debris flow, the total amount of solid material flushing, and the dynamic critical depth discriminant model of solid matter are analyzed. The results show that it is often used to measure the relevant indicators of debris flow solid matter, dynamic reserves and the total amount of solid matter flushing. The estimation methods are mostly to establish mathematical models or fitting formulas, lack of clear physical mechanism, universality and the measurement accuracy is low; and The concept of movable solid matter based on the existing problems just circumvents this problem, the existing research results can provide theoretical support for the establishment of its measurement method. Finally, the future research of debris flow solid source can be carried out:①In-depth study on the physical and mechanical mechanism of debris movable solid matter; ②Research on the spatial distribution of debris source solid source; ③Development of debris flow solid matter geotechnical characteristics research on the evolutionary law presented by the passage of time .