The invention discloses a debris flow risk degree evaluation method. The method comprises a step of determining the characteristic parameters associated with debris flow three elements, a step of establishing the comprehensive information evaluation system of the three elements, obtaining a three-element initial information evaluation matrix, and calculating the information entropy of the three elements through matrix operation and an entropy method, a step of establishing a debris flow information entropy model, taking three sub information entropy as an input factor, through BP neural network effect, and outputting debris flow information entropy, a step of defining a debris flow risk degree level standard according to the relation between the information entropy theory and the fact whether debris flow occurs, and carrying out risk degree evaluation on a search object. The invention discloses a debris flow probability model, the mutual interaction mechanism of debris flow three elements in a debris flow inoculation process can be comprehensively reflected, the complex nonlinear and dynamic processes of debris flow can be represented, the risk degree of the research object (single channel/regional debris flow) can be forecasted.