The purpose of this study was to investigate elementary students’ cognition of debris flow. A self-designed “questionnaire of cognition of debris flow” was utilized to collect the empirical data. The sampling method was stratified sampling combined with cluster sampling and the target population was the fifth- and sixth-grade students of public elementary schools in the central Taiwan, including the districts of Taichung County, Taichung City, Nantou County and Changhua County. A total of 1136 effective subjects was acquired. The primary findings of this research are as follows. First, students correctly answered 76% questions on average in the questionnaire. Their scores in the dimensions of “disaster of debris flow” and “prevention of debris flow” are higher than those of “characteristics of debris flow” and “formation factors of debris flow”. Second, students’ cognition of debris flow show no significant difference in different grades, different genders, and different social economic status of family. Third, students in the disaster area of debris flow gained significantly higher scores than those outside the disaster area. Finally, the researchers suggested that the disaster education of debris flow can be included in the teaching materials of elementary schools such that students’ cognition of debris flow can be enhanced.