The invention discloses a probability identifying method for debris flows in a mountainous strong shock area. The method includes spatial identification and time identification of the debris flow activities, wherein the spatial identification of the debris flow activities comprises identification based on sectorial debris flow accumulation area and identification based on the debris flow accumulation features; according to the spatial identification of the debris flow activities, debris flows in the mountainous strong shock area can be divided into a harmful object and a harmless object; the identification based on the debris flow accumulation features is adopted on the harmful object; the identification based on the sectorial debris flow accumulation area is adopted on the harmless object, wherein according to the identification based on the sectorial debris flow accumulation area, on the basis of the ratio of the sectorial debris flow accumulation area to a drainage area, a debris flow scale index is obtained, and the probability of the debris flows is identified through the debris flow scale index; the time identification of the debris flow activities is based on the activity time of earthquakes, and correlates a period after an earthquake with the probability of the debris flows. According to the probability identifying method for the debris flows in the mountainous strong shock area, a result based on the data analysis of observation and statistics is obtained, the method is scientific and operable, and the result is reliable.