Taking the actual examples, the author pointed out that the misunderstanding of the broken circle in the process of applying, The authors came to the proper use of the three principles of the bro- ken circle method as follow ;(1)breaking the smallest circle; ( 2 ) the broken line can not be re- used, (3)only break the arrow that stream into the arrow. Mastering the three principles of the bro- ken circle analysis method could not only make the engineering staff and teachers, students use cor- rectly the broken circle method to distinguish the double-arrow network critical path reference, but also extend the application of broken circle method.