The purpose of this study is to explore the recognition of the machine warning pictogram by students who are in junior high school age. Firstly, the Interview Survey is used to discuss with the frontline teachers the wrong behaviors that students easily to make. Then the questionnaire is designed and the confusion matrix is established based on the statistical results. Compare the recognition rate and confusion rate of junior high school students to different types of machine warning pictograms. Finally, analysis and classify several design principles, such as you need to pay attention the relationship between the shape and the image and the visibility of the image elements when you design the warning pictogram. If there is a body part, movement, prohibition symbol, machine or concrete symbol, it is easy to produce high recognition. When defining the meaning of the indication, too many keywords will lead to out of focus and make a confusion. It is recommended to use a simple and powerful word to interpretation the basis of design.