Abstract: The flip-flop screen can operate with self-cleaning function with its screen surface free from clogging when used for treating wet and sticky fine coal. The paper introduces the working principle of the flip-flop screen. Following an introduction to the basic structure of the LIWELL flip-flop screen, the paper goes to analyze the working principle of the screen′s drive system from the angle of its crank-guide mechanism. After that the author introduces the structural features of the BINDER flip-flop screen and makes an analysis of its vibrating principle using mechanical model. Result of analysis shows that: for the LIWELL version, the amplitude and speed of the outer screenbox are closely related to the length and speed of the crank; while for the BINDER screen, when its actual working frequency is close to the theoretical value, a larger stable amplitude can be imparted to its main and floating screen boxes with a smaller exciting force.